bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ca2+ influx into identified leech neurons induced by 5‐hydroxytryptamine
Authors: Dierkes Paul Wilhelm , Schlue Wolf‐Rüdiger 
Published: September 2004

AbstractThe role of 5‐hydroxytryptamine (5‐HT, serotonin) in the control of leech behavior is well established and has been analyzed extensively on the cellular level; however, hitherto little is known about the effect of 5‐HT on the cytosolic free calcium concentration ([Ca2+]i) in leech neurons. As [Ca2+]i plays a pivotal role in numerous cellular processes, we investigated the effect of 5‐HT on [Ca2+]i (measured by Fura‐2) in identified leech neurons under different experimental conditions, such as changed extracellular ion composition and blockade of excitatory synaptic transmission. In pressure (P), lateral nociceptive (N1), and Leydig neurons, 5‐HT induced a [Ca2+]i increase which was predominantly due to Ca2+ influx since it was abolished in Ca2+‐free solution. The 5‐HT‐induced Ca2+ influx occurred only if the cells depolarized sufficiently, indicating that it was mediated by voltage‐dependent Ca2+ channels. In P and N1 neurons, the membrane depolarization was due to Na+ influx through cation channels coupled to 5‐HT receptors, whereby the dose‐dependency suggests an involvement in excitatory synaptic transmission. In Leydig neurons, 5‐HT receptor‐coupled cation channels seem to be absent. In these cells, the membrane depolarization activating the voltage‐dependent Ca2+ channels was evoked by 5‐HT‐triggered excitatory glutamatergic input. In Retzius, anterior pagoda (AP), annulus erector (AE), and median nociceptive (N2) neurons, 5‐HT had no effect on [Ca2+]i. © 2004 Wiley Periodicals, Inc. J Neurobiol, 2005
On application of two superconvergent recovery procedures to plate problems
Authors: Boroomand B. , Ghaffarian M. , Zienkiewicz O. C. 
Published: September 2004

AbstractIn this paper a study is performed on application of two recovery methods, i.e. superconvergent patch recovery (SPR) and the recovery by equilibrium of patches (REP), to plate problems. The two recovery methods have been recognized to give similar results in adaptive solutions of two dimensional stress problems. While the former applies a least square fit over a set of values at the so called superconvergent points, the latter does not need any knowledge of such points and thus has a wider application especially in non‐linear problems. The formulation of REP is extended to Reissner–Mindlin plate problems. The convergence rates of the recovered fields of the gradients obtained from application of the two methods are compared using series of regular triangular and rectangular meshes for thick and thin plate solution cases. Assumed strain formulation based elements, i.e. the elements formulated by mixed interpolation of tensorial components, as well as conventional from of elements based on selective integration schemes are employed for the study.In order to investigate the possibility of any improvement in the results by adding equilibrium constraints to SPR, as some authors suggest for simple two‐dimensional problems, some weighted forms of such conditions are designed and added to the formulation. Comprehensive study has been given first by varying the weight terms to obtain the best enhanced results and then using the optimal values to investigate the effects of the constraints on the rate of convergence. It is observed that despite of the cost of this approach, due to the coupling of the gradient terms, no significant improvement is achieved. Copyright © 2004 John Wiley & Sons, Ltd.
Removal of ungrafted monomer from polypropylene‐graft‐maleic anhydride via supercritical carbon dioxide extraction
Authors: Clark Kelly , Lee Sunggyu 
Published: September 2004

AbstractThe removal of spent initiator, excess initiator and unbound monomer from newly synthesized polypropylene‐graft‐maleic anhydride (PP‐g‐MA) has typically been carried out using Soxhlet extraction. Standard solvents used in the Soxhlet process are xylene, toluene, acetone or methanol. These chemicals are not only hazardous to some degree, but also lead to undesirable maleic anhydride (MA) ring opening. This paper establishes that supercritical carbon dioxide (scCO2) extraction of residuals prevents anhydride ring opening and eliminates the need for post‐extraction vacuum‐drying of the copolymer product. An added benefit of this innovative process is that environmentally friendly carbon dioxide (CO2) is used in place of harmful solvents. The successful extraction of the residuals is established by thermogravimetric analysis (TGA), whereas FTIR spectroscopy is used to compare the anhydride content of Soxhlet‐extracted PP‐g‐MA to that of scCO2‐extracted copolymer. Polym. Eng. Sci. 44:1636–1641, 2004. © 2004 Society of Plastics Engineers.
Three‐dimensional polymer flow in the calender bank
Authors: Luther S. , Mewes D. 
Published: September 2004

AbstractThe velocity and pressure field that forms within the gap of a calender is numerically calculated. The numerical calculations are based on a decoupled calculation method for the free surface of the bank. The transport equations for mass and momentum are solved numerically. The position of the free surface of the bank is determined by shifting it until it matches a streamline. The resulting three‐dimensional velocity field gives the vortex patterns within the volume of the bank for fluids with non‐Newtonian and Newtonian rheological behavior. The shape of the free surface of the bank and its position are determined by the gap height, the circumferential speed of the rolls, the speed ratio, the feed mass flow into the gap and the rheological behavior of the polymer. Additionally, there are special requirements to be considered that determine the product quality, such as the thickness of the produced sheet, its uniformity and surface appearance, air inclusions and the mixing of the polymer. The calendering process itself requires limited operating windows for the variation of the process parameters in order to meet the product quality requirements. These operating windows are discussed and graphically plotted. Polym. Eng. Sci. 44:1642–1647, 2004. © 2004 Society of Plastics Engineers.
Rotational molding of polypropylene/ultra‐low‐density ethylene‐α‐olefin copolymer blends
Authors: Wang W. Q. , Kontopoulou M. 
Published: September 2004

AbstractThis work investigates the performance of blends in rotational molding, by using an industrially relevant system consisting of polypropylene (PP) and an ultra‐low‐density ethylene‐α‐olefin copolymer (or polyolefin plastomer, POP). Specifically, the effect of POP content and PP type on the sintering and densification behavior, as well as the rotomolded part properties and morphology, was examined. The sinter‐melting curves of these blends exhibited bimodality, due to the wide melting point difference between the two polymers. Increasing POP content resulted in higher sintering and densification rates, as well as improved impact properties and elongation at break, counteracted by lower stiffness. Selection of a polypropylene component with lower viscosity led to better sintering and densification characteristics, due to enhanced flow properties. Better overall performance in terms of mechanical properties was obtained when polypropylene/polyethylene impact copolymers, as opposed to a PP homopolymer, were used. Polym. Eng. Sci. 44:1662–1669, 2004. © 2004 Society of Plastics Engineers.
Spectroscopic, transport, and morphological studies of polyaniline doped with inorganic acids
Authors: Kulkarni Milind V. , Viswanath Annamraju Kasi , Marimuthu R. , Seth Tanay 
Published: September 2004

AbstractA conducting polymer, polyaniline, was synthesized by chemical polymerization using different inorganic acids, such as HCl, H2SO4, HClO4, HNO3, and H3PO4, as protonic acid media. The synthesized polymers were characterized using UV‐visible and FT‐IR spectroscopy. A granular type of morphology was observed under SEM for HCl, HNO3, and H3PO4 doped polyanilines. However, HClO4 doped polyaniline shows the folded lamellar structure derived from the fibers. The thermal stability of these polymers was investigated with the help of thermogravimetric (TG/SDTA) analysis. The formation of a greater fraction of the conducting emeraldine salt phase is observed in HClO4 as a protonic acid media. The thermal stability of H3PO4 doped material is found to be better as compared with other acids. An increase in conductivity with an increase in temperature was observed in all the samples except for HClO4 doped polyaniline. Polym. Eng. Sci. 44:1676–1681, 2004. © 2004 Society of Plastics Engineers.
Investigation of phase behavior during melt processing of novel inorganic‐organic polymer hybrid material
Authors: Guschl Peter C. , Otaigbe Joshua U. , Loong Chun‐Keung 
Published: September 2004

AbstractThe phase behavior of novel, binary organic‐inorganic hybrids consisting of an ultra‐low Tg tin‐based phosphate glass (Pglass) and polystyrene (PS) was investigated. Dynamic mechanical analysis (DMA) revealed that the glass transition peaks of the PS changed slightly with Pglass volume fraction, leading to a broad peak at the phase inversion point. The phase inversion and degree of phase continuity of the hybrid were studied through solvent extraction, optical/scanning electron microscopy, and dynamic rheology. The Jordhamo and Utracki viscosity ratio models provided reliable estimates of the inversion point. Torque rheometry revealed a trend toward linear additivity within the temperature range 200°C–230°C. Small‐angle neutron scattering experiments gave further evidence of the hybrid phase incompatibility. The results of this study point to a promising new class of blend materials with the potential to present a unique combination of properties impossible to achieve with classical polymer blends. Polym. Eng. Sci. 44:1692–1701, 2004. © 2004 Society of Plastics Engineers.
Effects of ZnO nano particles on thermal stabilization of polymers
Authors: Cho Kwang Soo , Hong Jung‐Il. , Chung Chan I. 
Published: September 2004

AbstractIt was reported that a nanocrystal ZnO had a thermal stabilizing effect for branched low‐density polyethylene (BLDPE). In this study, the thermal stabilizing effect of the nanocrystal ZnO was studied in more detail in comparison to a conventional, micron‐size ZnO using several polymers and a common antioxidant. The experimental results in this investigation suggest that the nanocrystal ZnO particles have different surface properties from micron‐size particles because of their extremely small size, and the particular surface properties are responsible for the thermal stabilizing effect. Polym. Eng. Sci. 44:1702–1706, 2004. © 2004 Society of Plastics Engineers.
Influence of ionomeric compatibilizers on the morphology and properties of amorphous polyester/polyamide blends
Authors: Gemeinhardt Gregory C. , Moore Ashley A. , Moore Robert B. 
Published: September 2004

AbstractThe utilization of sulfonated polyester ionomers as minor‐component compatibilizers in blends of an amorphous polyester and polyamide was investigated. The blends were prepared using twin‐screw extrusion and compared to solution blends to investigate the effect of elevated temperatures and shear mixing on blend miscibility and/or phase behavior. The phase domain sizes of the solution blends with respect to ionomer content were studied using small angle light scattering (SALS) and phase contrast optical microscopy. The thermal and mechanical properties of the extruded blends were investigated using dynamic mechanical analysis (DMA) and tensile testing while the morphology was investigated using environmental scanning electron microscopy (ESEM). The interactions between the sulfonate group of the ionomer and the polyamide were characterized using FT‐IR spectroscopy. Binary blends of the amorphous polyester and polyamide were immiscible with poor mechanical properties, while blends containing the polyester ionomer as a minor‐component compatibilizer showed a significant reduction in the dispersed domain sizes and enhanced ultimate mechanical properties. The compatibilization mechanism is attributed to specific interactions between the sulfonate groups on the polyester ionomer and the amide groups of the polyamide. Polym. Eng. Sci. 44:1721–1731, 2004. © 2004 Society of Plastics Engineers.
Scratch deformation characteristics of micrometric wollastonite‐reinforced ethylene‐propylene copolymer composites
Authors: Dasari A. , Misra R. D. K. , Rohrmann J. 
Published: September 2004

AbstractThe scratch deformation behavior of neat and wollastonite‐containing ethylene‐propylene copolymer composites has been studied by electron microscopy and atomic force microscopy techniques. The study indicates that the severity of plastic deformation during scratch testing in reinforced ethylene‐propylene copolymers is a function of debonding/detachment of wollastonite mineral particles from the ethylene‐propylene matrix. The resistance to scratch deformation was evaluated in terms of scratch hardness, scratch depth, average scratch roughness, and change in gray level before and subsequent to scratching. The data suggests that resistance to scratch deformation follows the sequence: coated + coupled wollastonite‐containing EP copolymer > fine wollastonite‐containing EP copolymer > coated wollastonite‐containing EP copolymer > coarse wollastonite‐containing EP copolymer > neat EP copolymer. EP copolymer containing coated wollastonite and coupling agent is characterized by highest scratch hardness and minimum scratch depth and scratch roughness. The visibility of scratch, quantified in terms of gray level, suggests that coated + coupled wollastonite‐containing copolymer exhibits significantly reduced susceptibility to stress whitening, and is characterized by a lower gray level in the scratch‐deformed regions. In the present case of wollastonite‐containing copolymer composites, the resistance to scratch deformation follows a trend similar to that of gray level or scratch visibility. Polym. Eng. Sci. 44:1738–1748, 2004. © 2004 Society of Plastics Engineers.
Relating the molecular structure and crystallization behavior of polypropylene
Authors: Chen Jianfeng , Yin Li , Yang Xiaoniu , Zhou Enle 
Published: September 2004

AbstractThe crystallization behavior of two polypropylene (PP) resins as used for biaxially oriented polypropylene (BOPP) and general injection mold applications, respectively, has been intensively investigated and compared by means of polarized light optical micrography (POM), differential scanning calorimetry (DSC), conventional transmission electron microscopy (TEM), and high resolution transmission electron microscopy (HRTEM). It is found that both molecular weight distribution and isotacticity of polypropylene strongly affect its crystallization characteristics, e.g., the number of crystal nuclei at the initial stage, crystallization dynamics, the morphology, size and perfection of crystals in the final product, and so on. The results indicate an appropriate molecular structure is vital in producing high‐quality BOPP film. Polym. Eng. Sci. 44:1749–1754, 2004. © 2004 Society of Plastics Engineers.
Electrically conductive thermoplastic blends for injection and compression molding of bipolar plates in the fuel cell application
Authors: Mighri Frej , Huneault Michel A. , Champagne Michel F. 
Published: September 2004

AbstractThis study aimed at developing highly conductive, lightweight, and low‐cost bipolar plates for use in proton exchange membrane fuel cells. Injection and compression molding of carbon‐filled polypropylene, PP, and polyphenylene sulfide, PPS, were used to fabricate the bipolar plates. Loadings up to 60 wt% in the form of graphite, conductive carbon black, and carbon fibers were investigated. The developed compositions have a combination of properties and processability suitable for fuel cell bipolar plate manufacturing, such as good chemical resistance, sufficient fluidity, and good electrical and thermal conductivity. Two bipolar plate designs were successfully fabricated by molding the gas flow channels over aluminum plates to form a metallic/polymer composite plate or simply by direct injection molding of the conductive polymer composite. For the first design, overall plate volume resistivities of 0.2 and 0.1 Ohm‐cm were respectively attained using PP and PPS based blends as the conductive overmolded layer. A lower volume resistivity of around 0.06 Ohm‐cm was attained for the second design with injection molded plates made of the PPS‐based blend. Polym. Eng. Sci. 44:1755–1765, 2004. © 2004 Society of Plastics Engineers.
Exfoliation and dispersion enhancement in polypropylene nanocomposites by in‐situ melt phase ultrasonication
Authors: Lee E. C. , Mielewski D. F. , Baird R. J. 
Published: September 2004

AbstractA novel process using ultrasonics to enhance the exfoliation and dispersion of clay platelets in polypropylene‐based nanocomposites has been proposed and investigated. The materials studied were isotactic polypropylene of various molecular weights reinforced with organophilic montmorillonite clay (nanoclay) at 4–6 wt% loadings. X‐ray diffraction (XRD) and rheological measurements, on a model system of nanoclay in mineral oil, were first used to determine ultrasonic energy requirements. The effectiveness of the proposed ultrasonic processing technique on polypropylene nanocomposites was evaluated by XRD and transmission electron microscopy (TEM). The effects of added maleic anhydride–grafted polypropylene compatibilizer, polypropylene molecular weight, and pretreatment of the nanoclays on the nanocomposite exfoliation were also investigated. Results indicate that ultrasonic processing of polymer nanocomposites in the melt state is an effective method for improving exfoliation and dispersion of nanoclays. Issues regarding molecular weight degradation, optimization, mechanical properties, and continuous processing are beyond the scope of the present study and are currently being investigated in our laboratory. Polym. Eng. Sci. 44:1773–1782, 2004. © 2004 Society of Plastics Engineers.
Thermal and X‐ray powder diffraction studies of aliphatic polyester dendrimers
Authors: Ropponen Jarmo , Tuuttila Tero , Lahtinen Manu , Nummelin Sami , Rissanen Kari 
Published: September 2004

AbstractThe syntheses and thermal and X‐ray powder diffraction analyses of three sets of aliphatic polyester dendrimers based on 2,2‐bis(hydroxymethyl)propionic acid as a repeating unit and 2,2‐dimethyl‐1,3‐propanediol, 1,5‐pentanediol, and 1,1,1‐tris(hydroxymethyl)ethane as core molecules are reported. These dendritic polyesters were prepared in high yields with the divergent method. The thermal properties of these biodendrimers were evaluated with thermogravimetric analysis and differential scanning calorimetry. The thermal decomposition of the compounds occurred around 250 °C for the hydroxyl‐ended dendrimers and around 150 °C for the acetonide‐protected dendrimers. In addition, the crystallinity of the lower generation dendrimers was evaluated with X‐ray powder diffraction. The highest crystallinity and the highest melting points were observed for the first‐generation dendritic compounds. The higher generation dendrimers showed weaker melting transitions during the first heating scan. Only the glass‐transition temperatures were observed in subsequent heating scans. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5574–5586, 2004
Adolescent voting for right‐wing extremist parties and readiness to use violence in political action: parent and peer contexts
Authors: Kuhn Hans Peter 
Published: September 2004

ABSTRACTAlmost all shapes of adolescent risky and deviant behaviour take place in the context of peer‐relations. The present study examined the role of parents and peer‐relations with respect to two indicators of deviant political development. In the fall 1998, directly after the German parliamentary elections, 1309 East German adolescents were asked about their voting for a right‐wing extremist party and their readiness to use violence in political action. Friend′s voting was a strong predictor of individual voting for a right‐wing extremist party, particularly when the friend was the best friend with a reciprocal nomination, and when the friends frequently communicated about political themes. In addition, voting behaviour and willingness to use violence were associated with membership in peer groups who met frequently. Finally, the violence‐disposed adolescents spent more of their spare time with peers and less with their parents. Similarities of our results with the findings of research on deviant behaviour in non‐political areas support the idea that deviant political behaviour could be an expression of a problematic life situation.
Significant difference in knowledge between English and Danish psychiatrists
Authors: Hansen Lars , McDonald John W. 
Published: September 2004

AbstractPurposeThe purpose of the study was to investigate if differences in levels of knowledge existed between Danish and English training and specialist psychiatrists. This is important in the context of the free (and growing) movement of the medical workforce across European Union (EU) countries’ borders.MethodsA complete balanced two-way factorial study design was used. Ten training and ten specialist psychiatrists were recruited in each country from reputable, university hospitals. They answered 50 multiple choice questions (MCQs), translated into the appropriate language, consisting of four subcategories of questions: psychology (15 MCQs), psychopharmacology (10 MCQs), neuroscience (five MCQs) and psychopathology (20 MCQs). No memory or other types of aids were allowed at the knowledge test. A two-way analysis of variance was used to analyse the total knowledge score (number of correct answers) and the component subscores. Levene’s test of equality of error variances was used to test for variance homogeneity.ResultsThere were significant differences in total knowledge and psychology knowledge by country and level of training. UK doctors scored 3.10 points higher than Danish doctors, with 95% confidence interval (0.97, 5.23). The knowledge of the specialists was also significantly superior to that of the training psychiatrists, with 2.30 higher score, 95% confidence interval (0.17, 4.43). In the sub-categories only the scores in the psychology section were significantly different. UK doctors scored 2.30 higher than Danish doctors, with 95% confidence interval (1.15, 3.45). Specialists scored 1.20 higher than non-specialists with 95% confidence interval (0.05, 2.35).ConclusionsThe results indicate that there is a significant difference in level of knowledge between psychiatrists in these two EU-countries, England and Denmark. This difference seemed to be chiefly the result of different knowledge of psychology. The disparity could be a result of the fundamentally different post-graduate training system in psychiatry in the two countries. Surprisingly, the differences in total knowledge and psychology knowledge between countries were larger than the differences between levels of training. The difference in knowledge is worrying taking into consideration that there is free movement of the workforce, including doctors, across the EU. The results here need further confirmation in future studies with greater numbers, more countries involved and perhaps additional measurements to MCQs.