bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation de l'exploitation d'une visite au zoo par le traitement graphique
Authors: Girault Yves , Rukingama Thérèse , Sonnois  , Toumade
Published: June 2010

Evaluation of the exploitation of a visit to a zoo by graphic treatment.

It is important for visits to a zoo to be related to a teaching programme centred on observation. Children may find it difficult in the classroom to make good use of the data they have collected. We have experimented with "Matrix", a computer programme of graphic treatment, to see how it could be used with primary school children.
La naissance du concept d'écosystème
Authors: Drouin Jean-Marc
Published: June 2010

Origin of the Ecosystem concept.

The ecosystem concept which was introduced by Tansley in 1935 does not simply proceed from the application to ecology of a "general systems theory" but belongs to the intrinsic history of ecology and of biogeography. The theoretical debates arising from it bring into play from the beginning a series of relations between man and nature, the living and non-living, unity and multiplicity. Three texts have played an important part in the development of this concept : a pioneer text by S.A. Forbes (1887), the fundamental text of Tansley (1935), and a first quantitative approach to energetic relations within the ecosystem (Lindeman, 1942).
Notions physiques, objets techniques et structures mathématiques, à propos de la température au cycle moyen
Authors: Pierrard Marie-Anne
Published: June 2010

Les liens entre la physique et les mathématiques sont analysés dans deux activités de classe du cycle moyen de l'école élémentaire où la température intervient : graduation d'un thermomètre à liquide et mélanges d'eau chaude et d'eau froide. il ressort que la référence à la règle graduée joue un rôle essentiel, mais qu'elle peut masquer une propriété du thermomètre : donner la température du milieu dans lequel il se trouve. L'étude des mélanges d'eau chaude et d'eau froide montre comment l'utilisation d'un support spatial, la droite des températures, permet d'arriver à une formulation de la relation calorimétrique.

Cet article présente les résultats d'une thèse de 3ème cycle, soutenue à l'Université de Paris VII en 1982.
Chaleur, température, changements d'état
Authors: Laval Annie
Published: June 2010

Le premier objectif de ce travail était de rechercher comment les enfants entrant en classe de 6e conçoivent les phénomènes physiques intervenant dans leur vie quotidienne, ainsi que l'influence ultérieure de l'enseignement sur ces Idées préalables . Les enquêtes menées dans ce but auprès des élèves de collège sont rapportées dans une première partie.

Ensuite compte tenu des résultats précédents, des propositions sont faites sur la façon d'adapter la pédagogie à l'état d'esprit des enfants. Quelques essais d'enseignement ont permis de mieux cerner les points de résistance et de tester les notions qui sont accessibles aux élèves des premières années du collège
Sur la caractérisation des objectifs de l'initiation aux sciences physiques
Authors: Martinand Jean-Louis
Published: June 2010

Cet article est principalement constitué de larges extraits du texte de synthèse rédigé par Jean-Louis Martinand, pour présenter les lignes de force de sa thèse d'état soutenue en mai 1982 à l'Université d'Orsay.

A partir de ses pratiques d'innovation et de recherche conduites dans trois domaines :

- l'élaboration d'un enseignement sur les techniques de fabrication pour les élèves de 13 -14 ans.

- une réflexion sur la notion d'élément chimique en 5ème

- l'approche de la notion de dureté en 6ème,

Il dégage deux notions-clés pour la didactique des sciences physiques : celle de pratiques sociales de référence et celle d'objectif-obstacle.
Les modèles particulaires
Authors: Genzling Jean-Claude
Published: June 2010

Particulate models.

When studying physical transformations. 9-12 year-old pupils of "Cours Moyen" are asked to undertake a modelisation activity i.e. to construct a model, use it to interpret physical phenomena already observed in another context, modify it, use it for prediction. An activity of this sort can play a central part in the building up of knowledge and of scientific method.
Modèle particulaire et activités de modélisation en classe de quatrième
Authors: Chomat Alain , Larcher Claudine , Méheut Martine
Published: June 2010

Particulate model and modélisation activities in 4th form (13-14 year-olds).

What modelisation activities can pupils of this level cany out ? In the context of the introduction of a particulate model of matter, we present a teaching sequence which enables pupils to put into practice modélisation activities : building, adapting and applying a model.

This is achieved by introducing an axiom the terms of which form a basis for systemising the explanations of different phenomena.

Pupils are led to produce and to interpret graphic representations, and the relevancy of these in accounting for the phenomena in question is discussed by the class.
The stochastic quantization method and its application to the numerical simulation of volcanic conduit dynamics under random conditions
Authors: Peruzzo E. , Barsanti M. , Flandoli F. , Papale P.
Published: June 2010

Abstract. Stochastic Quantization (SQ) is a method for the approximation of a continuous probability distribution with a discrete one. The proposal made in this paper is to apply this technique to reduce the number of numerical simulations for systems with uncertain inputs, when estimates of the output distribution are needed. This question is relevant in volcanology, where realistic simulations are very expensive and uncertainty is always present. We show the results of a benchmark test based on a one-dimensional steady model of magma flow in a volcanic conduit.
Evidence for disruption of sphingolipid metabolism as a contributing factor in the toxicity and carcinogenicity of fumonisins
Authors: Riley Ronald T. , Wang Elaine , Schroeder Joseph J. , Smith Elizabeth R. , Plattner Ronald D. , Abbas Hamed , Yoo Hwan‐Soo , Merrill Alfred H.
Published: June 2010

Fumonisins are inhibitors of the biosynthesis of sphingosine and more complex sphingolipids. In eucaryotic cells, fumonisin inhibition of sphingolipid biosynthesis is a result of inhibition of the enzyme ceramide synthase. Large increases in free sphinganine concentration in plant and animal cells are observed within a few hours after exposure to fumonisins and/orAltemariatoxins (AAL‐toxins). Some of the sphinganine is metabolized to other bioactive intermediates, and some is released from cells. In animals, free sphinganine accumulates in tissues and quickly appears in blood and urine. Free sphingoid bases are toxic to most cells, and complex sphingolipids are essential for normal cell growth. Fumonisin B1stimulates sphinganine‐dependent DNA synthesis in Swiss 3T3 cells, but is mitoinhibitory in other cell types. In cultured cells the accumulation of bioactive long‐chain sphingoid bases and depletion of complex sphingolipids are clearly contributing factors in growth inhibition, increased cell death, and (in Swiss 3T3 cells) mitogenicity of fumonisins. While disruption of sphingolipid metabolism directly affects cells, it may indirectly affect some tissues. For example, fumonisin B1impairs the barrier function of endothelial cells in vitro. Adverse effects on endothelial cells could indirectly contribute to the neurotoxicity and pulmonary edema caused by fumonisins. It is hypothesized that fumonisin‐induced changes in the sphingolipid composition of target tissues could directly or indirectly contribute to allFusarium moniliforme‐associated diseases.
Studies on the reproductive effects of fusarium moniliforme culture material in rats and the biodistribution of [14c]fumonisin B1 in pregnant rats
Authors: Voss Kenneth A. , Bacon Charles W. , Norred William P. , Chapin Robert E. , Chamberlain William J. , Plattner Ronald D. , Meredith Filmore I.
Published: June 2010

Fumonisins are mycotoxins produced by Fusarium moniliforme and other Fusarium species. They are commonly found in corn and corn‐based foodstuffs. Fumonisins inhibit sphingolipid (SL) biosynthesis, alter cellular SL profiles, and thus may affect cell proliferation and differentiation, both of which are important processes for reproduction. However, there are few reports of the effects of F. moniliforme or fumonisins on mammalian reproduction or development. To study the reproductive effects of this fungus, diets formulated with culture material of toxic F. moniliforme strain MRC 826 (CM) to provide 0, 1, 10, or 55 ppm fumonisin B1 (FB1) were fed to male and female rats beginning 9 and 2 weeks before mating, respectively, and continuing throughout mating, gestational, and lactational phases of the study. CM caused nephropathy, typical of FB1, in males fed ≥10 ppm and females fed 55 ppm FB1. No significant reproductive effects were found in males (n = 12/group), dams, and fetuses examined on gestation day 15 (G15) (n ≥ 8/group), or dams and litters through day 21 postpartum (n ≥ 9/group). Litter weight gain in the 10 or 55 ppm FB1 groups was slightly decreased; however, gross litter weight and physical development of offspring were not affected. Altered SL ratios indicative of fumonisin exposure, specifically increased sphinganine to sphingosine ratios, were found in the livers of dams from the 55‐ppm FB1 group on G15. However, SL ratios of abdominal slices, containing liver and kidney, of fetuses from control and high‐dose litters did not differ. In a second experiment, two dams were injected intravenously on G15 with 101 μg[14C]FB1 (3.179 × 105 dpm). After 1 hr, which allowed for ca. 98% of the dose to be cleared from the maternal blood, negligible amounts of radioactivity were found in the fetuses. Together, these results indicate that the CM, and by inference FB1, did not have significant reproductive effects at doses which are minimally toxic, and further suggest that little in utero FB1 exposure occurred through G15.
Intravenous fumonisin B1 induces cell proliferation and apoptosis in the rat
Authors: Lim Chae Woong , Parker Helen M. , Vesonder Ronald F. , Haschek Wanda M.
Published: June 2010

In the rat, the target organs of fumonisin B1, a mycotoxin produced by Fusarium moniliforme, are the kidney and liver. Fumonisin B1 is also hepatocarcinogenic in the rat and is associated epidemiologically with esophageal cancer in humans. We investigated the effect of a single intravenous dose of fumonisin B1 on cell proliferation, lesion development, and glutathione status in the major target organs of the rat. Male Sprague‐Dawley rats were injected intravenously with fumonisin B1 at 0 or 1.25 mg/kg and were euthanized at 12 hr or, 1, 2, 3, or 5 days. An intraperitoneal injection of 5‐bromo‐2′‐deoxyuridine at 100 mg/kg was given 90 min prior to euthanasia. In fumonisin B1 treated rats, serum cholesterol and serum urea nitrogen were elevated; however, the activity of hepatic enzymes was unaffected. Hepatic and renal glutathione concentrations were depressed at 12 and 24 hr, respectively, with subsequent recovery. Histologic changes were most prominent in the outer medulla of the kidney, with cell proliferation and apoptosis followed by nephrosis. Cell proliferation also occurred in the liver and esophagus, but in the absence of tissue injury. The labeling index peaked on day 1 for the liver and on day 3 for the esophagus. These results confirm that the primary target organ of fumonisin B1 in the rat is the kidney and support the concept that fumonisin B1‐induced mitogenesis may be the mechanism of carcinogenesis.
Cytochalasin W, a new 24‐oxa[14]cytochalasan from phoma exigua var. heteromorpha
Authors: Evidente Antonio , Capasso Renato , Vurro Maurizio , Bottalico Antonio
Published: June 2010

A further cytochalasin was isolated from liquid culture filtrates of Phoma exigua var heteromorpha together with cytochalasins U and V and other well‐known cytochalasins. The metabolite, named cytochalasin W, was characterized by spectroscopic and chemical methods as a new 24‐oxa[14]cytochalasan, bearing a formyl group on the macrocyclic ring. Cytochalasin W showed toxic activity in the brine shrimp assay.
Toosendanin facilitates [3H]noradrenaline release from rat hippocampal slices
Authors: Hua‐Yu Huang , Cheng‐Wen Zhou , Yu‐Liang Shi
Published: June 2010

Slices of hippocampus of the rat, preincubated with [3H]noradrenaline ([3H]NA), were used to investigate the effects of toosendanin on the release of [3H]NA. Toosendanin potently enhanced spontaneous 3H outflow. Seventy‐four percent of the enhancement was inhibited by reserpine pretreatment. The toosendanin‐induced 3H overflow was in a concentration‐dependent manner (5–60 μM) both in the presence and absence of extracellular calcium. Under Ca2+‐free conditions, the effect of toosendanin on 3H outflow was unchanged by TTX, but inhibited by Ca2+‐chelator BAPTA‐AM; dantrolene sodium failed to affect the toosendanin‐induced 3H outflow, while 3,4‐diaminopyridine showed an additive effect on the outflow with this substance. The findings suggest that in the absence of extracellular Ca2+, toosendanin enhances [3H]NA release through the liberation of intracellular Ca2+ stores.
Partial purification and characterization of an esterase from fusarium sporotrichioides
Authors: Park Joung J. , Chu Fun S.
Published: June 2010

Kinetics analysis of the growth of Fusarium sporotrichioides T‐424 at 15°C and 25°C in liquid culture for 35 days revealed that production of deacetylated trichothecenes was associated with an increased activity in fungal esterases High temperature (25°C) favored enzyme production and enhanced esterase activity. Electrophoresis of crude extracts from the mycelia of F. sporotrichioides T‐424 with carboxylesterase staining revealed that several esterases were produced by the fungus. Four carboxylesterase isoenzymes (I‐IV) were separated on a DEAE‐Sephadex anion exchange column. Type (III) esterase, having activities with the substrate 4‐nitrophenylacetate and acetanilide, as well as hydrolytic activity for T‐2 toxin and acetyl‐T‐2 toxin, was partially purified with ammonium sulfate precipitation, immunoaffinity column chromatography, and DEAE‐Sephadex A‐50 chromatography. The esterase (III) had a molecular weight around 68 kDa in SDS‐PAGE. For the deacylation of T‐2 toxin and acetyl‐T‐2 toxin, type (III) esterase had a high specificity for the acetyl group at the C‐3 and C‐4 positions The Km values for acetyl‐T‐2 and T‐2 toxin were found to be 41.35 μM and 0.38 μM, respectively. The Km value for the acetyl group at C‐3 is 110 times greater than for that at C‐4
Effects of ochratoxin A on the rat immune system after perinatal exposure
Authors: Thuvander Ann , Funseth Eva , Breitholtz‐Emanuelsson Anna , Hallén Ira Palminger , Oskarsson A.
Published: June 2010

Effects on the immune system after perinatal exposure to ochratoxin A (OA) were studied in Sprague‐Dawley rats after single or repeated exposure of the dams. In a short‐term study, dams with litters were given a single dose of OA (0, 10, 50 or 250 μg/kg body weight) on day 11 of lactation. The effects on cell numbers in spleen and thymus and on the mitogen responses of lymphocytes were evaluated in the suckling pups on day 14 of lactation. The proliferative response of splenocytes to the T‐cell mitogen Concanavalin A (Con A) was significantly stimulated in pups from dams given 10 or 50 μg OA/kg body weight as compared to control pups. In addition, proliferation of thymocytes in response to Con A was stimulated in pups from dams exposed to 50 μg OA/kg body weight.

In a long‐term, cross‐fostering study comparing pre‐ and postnatal exposure, half of the dams received 50 μg OA/kg body weight 5 days a week by gastric intubation 2 weeks before mating, during gestation and then 7 days a week until weaning. Effects on immune parameters were studied in the pups on day 14 of lactation and at 13 weeks of age. Suppressed mitogenic responses were seen to both lipopolysaccharide (LPS) and Con A in prenatally exposed pups sampled on day 14 of lactation. At 13 weeks the response of splenocytes to LPS was still impaired. The primary antibody response to a viral antigen was also lower in the prenatally exposed pups than in the control pups. These effects on the immune response were not seen in the groups of pups exposed postnatally or both pre‐ and postnatally, although blood concentrations of OA were higher in these groups at the time of the first sampling. This indicates that the decrease in proliferation and antibody production resulted from prenatal modulation of the immune system.

The results show that prenatal exposure to relatively low doses of OA may induce immunosuppression. In contrast, short‐term exposure of suckling pups to OA via the milk stimulates the proliferative responses of lymphocytes to polyclonal activation.
Amino acid sequence of peptidyl‐prolyl isomerase a of fusarium sporotrichioides
Authors: Chow Lu‐Ping , Kamo Masaharu , Ueno Yoshio , Tsugita Akira
Published: June 2010

Peptidyl‐prolyl‐cis‐trans isomerase catalyzes the interconversion of the cis and trans isomers of the proline‐containing polypeptides and the folding process of proteins. This protein was known to be cyclophilin which has high binding affinity for cyclosporin A, a cyclic undecapeptide of fungal origin with potent immunosuppressive property agent. The two cytosolic peptidyl‐prolyl‐isomerases were found from Fusarium sporotrichioides. The amino acid sequence of the major peptidyl‐prolyl isomerase a was determined by conventional sequencing methods; the protein with a calculated molecular mass of 19.7 kDa consisting of 179 amino acids. The comparison of the amino acid sequence of peptidyl‐prolyl‐isomerase from Fusarium with that of Nucerospora crassa revealed a significant degree of amino acid sequence homology (82.2%).
Influence of perinatal ochratoxin A exposure on the immune system in mice
Authors: Thuvander Ann , Dahl Petra , Breitholtz‐Emanuelsson Anna
Published: June 2010

The mycotoxin ochratoxin A (OA) is a well‐documented immunotoxic agent which affects both cellular and humoral immunity. In the present study, the effects of maternal exposure to single doses of OA during gestation or lactation were studied in Balb/c offspring. A single dose exposure of the dams to OA (500 μg/kg body weight) on day 16 of gestation resulted in decreased proliferation of splenic and thymic lymphocytes in response to mitogens in the pups at 15 days of age. Flow cytometry analysis of thymocyte subpopulations revealed lower percentages of mature CD4+cells and higher percentages of immature, double‐positive (CD4+CD8+) cells in the exposed pups. In contrast, a single exposure of the dams of OA on day 10 postpartum significantly increased the proliferative responsiveness of lymphocytes in the offspring when stimulated with B or T cell mitogens 3 days after the exposure. This effect was most prominent in the highest dose group (500 μg/kg body weight). The present results are in accordance with previous observations in rats, and show that the time of exposure significantly influences the immunotoxic effects of OA on the developing immune system in rodents.
Apoptotic cellular damage in mice after T‐2 toxin‐induced acute toxicosis
Authors: Ihara Tomomi , Sugamata Masao , Sekijima Masaru , Okumura Hiroki , Yoshino Naoto , Ueno Yoshio
Published: June 2010

By histopathologic, electron microscopic, and immunochemical observation, the mechanism of cellular death was investigated in thymus, spleen, and liver of mice given intraperitoneally sublethal doses of T‐2 toxin, a trichothecene mycotoxin. In the thymus and spleen of mice given 5.0 mg/kg body weight of T‐2 toxin and killed 12 hours later, a massive cellular destruction characterized by chromatin condensation was evident, and electron microscopy analysis revealed the presence of apoptotic bodies. In the liver of mice given 2.5 mg/kg of T‐2 toxin and killed 2 hours later, the induction of apoptotic cellular lesions was observed by electron microscopy, and Kupffer cells phagocytosed the apoptotic bodies. Such lesions were not observed in the mice killed 12 hours after receiving the toxin. In situ nick translation analysis (Tunel method) revealed DNA fragmentation in thymus, spleen, and liver shortly after administration of T‐2 toxin. As previously observed in vitro, these findings indicated that T‐2 toxin is a potent inducer of apoptotic cell death in thymus, spleen, and liver in vivo; especially in liver, apoptosis is induced rapidly as compared with the other tissues observed, and Kupffer cells play an important role for clearance of apoptosis. Nat. Toxins 5:141–145, 1997. © 1997 Wiley‐Liss, Inc.
Fabrication and Microstructure of C/Cu Composites
Authors: Liu Yiwen , Zhang Chengyu , Qiao Shengru , Yang Zhimao
Published: June 2010

C/Cu composites were prepared by a melting infiltration technique in vacuum. In order to improve the wettability between Cu and carbon fibers, Ti (8 wt.‐%) and Cr (1 wt.‐%) were added to the Cu alloy. Microstructures of the composites and interface between C and Cu were investigated by XRD, SEM, EDS and HRTEM. The results show that the Ti and Cr improved the wettability between Cu and CC preform and the infiltration ability of Cu into CC preform greatly. The prepared C/Cu composites are characterized as having good interface bonding and high density. In the process of infiltration, Ti and Cr concentrate on the boundary of carbon fiber. Formation of TiC results from the reaction of Ti and C between Cu and carbon fiber.
Localization Events and Microstructural Evolution in Ultra‐Fine Grained NiTi Shape Memory Alloys during Thermo‐Mechanical Loading
Authors: Schaefer Andreas , Wagner Martin Franz‐Xaver , Pelegrina Jorge Luis , Olbricht Jürgen , Eggeler Gunther
Published: June 2010

Subjecting a thin NiTi specimen to uniaxial tension often leads to a localized martensitic transformation: macroscopic transformation bands form and propagate through the specimen, separating it into regions of fully transformed martensite and original austenite. In the present study, the alternating current potential drop (ACPD) technique is used to analyze the change in electrical resistance of ultra‐fine grained NiTi wires subjected to a broad range of thermo‐mechanical load cases: (i) uniaxial tensile straining at constant temperatures (pseudoelastic deformation); (ii) cooling and heating through the transformation range at constant load (actuator load case); (iii) a combination of mechanical and thermal loading. We monitor the ACPD signals in several zones along the gauge length of specimens, and we demonstrate that a localized type of transformation is a generic feature of pseudoelastic as well as of shape memory deformation. Moreover, the ACPD signals allow to differentiate between temperature‐induced martensite (formed during cooling at no or relatively small loads), stress‐induced martensite, and reoriented martensite (formed under load at low temperatures).
Preparation and Tribological Properties of MoS2 Nanosheets
Authors: Wu Zhuangzhi , Wang Dezhi , Wang Yi , Sun Aokui
Published: June 2010

MoS2 nanosheets were successfully synthesized by a micro‐domain reaction method, employing a ball‐milled mixture of MoO3 and S as starting materials. The obtained MoS2 nanosheets are monodisperse, and the length and width are about 100 and 10 nm, respectively. Furthermore, the tribological performances of the as‐obtained MoS2 nanosheets were studied and possible optimized mechanisms were also proposed.
Ab‐initio‐Thermochemie fester Stoffe
Authors: Stoffel Ralf Peter , Wessel Claudia , Lumey Marck‐Willem , Dronskowski Richard
Published: June 2010

In diesem Aufsatz stellen wir einen auf elektronentheoretischen Rechnungen beruhenden Zugang zu einer quantenchemischen Thermochemie von Feststoffen vor. Zunächst gehen wir auf lokale und kollektive Atomauslenkungen ein und erläutern kurz den theoretischen Hintergrund. Die fundamentale Bedeutung der Phononen, ihre Dispersionsrelationen, ihre experimentelle Bestimmung und ihre Berechnung wird beleuchtet, gefolgt von der systematischen Konstruktion thermodynamischer Potentiale auf dieser Basis. Anschließend liefern wir eine Rechenanleitung sowie eine kritische Analyse der erzielbaren Genauigkeit und zeigen dann, wie verschiedene festkörperchemische Probleme so angegangen werden können. Dazu gehört die Berechnung atomarer Aktivierungsenergien in perowskitischen Oxiden, aber auch die Berücksichtigung berechenbarer Schwingungsfrequenzen zur Aufklärung von Kristallstrukturen. Dann behandeln wir die klassisch oft beschriebene Druck‐ und Temperaturpolymorphie von elementarem Zinn und nehmen eine energetische Klassifikation metastabiler Oxidnitride des Tantals vor. Schließlich weisen wir für Hochtemperatursupraleiter nach, wie die Rechnungen zur Evaluation unbefriedigend präziser thermochemischer Daten herangezogen werden können. Am Ende zeigen wir die momentanen Grenzen und die zukünftigen Herausforderungen der Theorie auf.
Microdroplets in Microfluidics: An Evolving Platform for Discoveries in Chemistry and Biology
Authors: Theberge Ashleigh B. , Courtois Fabienne , Schaerli Yolanda , Fischlechner Martin , Abell Chris , Hollfelder Florian , Huck Wilhelm T. S.
Published: June 2010

Microdroplets in microfluidics offer a great number of opportunities in chemical and biological research. They provide a compartment in which species or reactions can be isolated, they are monodisperse and therefore suitable for quantitative studies, they offer the possibility to work with extremely small volumes, single cells, or single molecules, and are suitable for high‐throughput experiments. The aim of this Review is to show the importance of these features in enabling new experiments in biology and chemistry. The recent advances in device fabrication are highlighted as are the remaining technological challenges. Examples are presented to show how compartmentalization, monodispersity, single‐molecule sensitivity, and high throughput have been exploited in experiments that would have been extremely difficult outside the microfluidics platform.
Homogeneous Gold Catalysis Beyond Assumptions and Proposals—Characterized Intermediates
Authors: Hashmi A. Stephen K.
Published: June 2010

Gold catalysis is a very active area in the field of catalysis research. New reactions are published every week, amazing changes in the connectivity are often observed, the number of applications in total synthesis is increasing …︁—but what are the mechanisms of these reactions? Sound information can be provided by knowledge about the intermediates of these reactions.
Mechanical behavior of carbon nanofibre‐reinforced epoxy composites
Authors: Rana Sohel , Alagirusamy R. , Joshi Mangala
Published: June 2010

Epoxy resins are widely used in a variety of applications because of their high chemical and corrosion resistance and good mechanical properties. But few types of epoxy resins are brittle and possess low toughness which makes them unsuitable for several structural applications. In this work, carbon nanofibres have been dispersed uniformly into the epoxy resin at a very low concentration (0.07 vol. %). Improvement of 98% in Young modulus, 24% in breaking stress and 144% in work of rupture was achieved in the best sample. The emphasis is on achieving uniform dispersion of carbon nanofibers into epoxy resin using a combination of techniques such as ultrasonication, use of solvent and surfactants. The fracture surfaces of the specimens were studied under scanning electron microscope to see the fracture mechanism of nanocomposites under tensile load and correlate it to the enhancement in their properties. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Synthesis and characterization of degradable triarm low unsaturated poly(propylene oxide)‐block‐polylactide copolymers
Authors: Yang Dongmei , Lu Qi , Fan Zhongyong , Li Suming , Tu Jianjun , Wang Wei
Published: June 2010

A series of novel degradable triarm poly(propylene oxide)‐block‐polylactide (PPO‐b‐PLA) copolymers was synthesized by ring‐opening polymerization of L‐lactide (LLA) or D,L‐lactide (DLLA) using low unsaturated PPO triols as macromolecular initiator. The chemical structures of the resulting copolymers were characterized by Fourier transform infrared (FTIR), gel permeation chromatography (GPC), and proton nuclear magnetic resonance (1H‐NMR) spectroscopy. Combination of FTIR, GPC, and NMR results confirmed the formation of PPO‐b‐PLA copolymers. One glass transition was observed by differential scanning calorimetry (DSC), suggesting good miscibility between PPO and PLA segments in the copolymers. DSC and wide‐angle X‐ray diffraction demonstrated that PPO‐b‐PLLA copolymers were semicrystalline materials, and the crystallinity increased with increasing the PLLA content. In contrast, PPO‐b‐PDLLA copolymers were totally amorphous. The PPO‐b‐PLA copolymers exhibited improved thermal stability when compared with PPO polyols according to thermogravimetric analysis. The thermal degradation behavior of the copolymers depended on the composition. Polyurethane foams were prepared by crosslinking PPO and PPO‐b‐PLA copolymers using isocyanate. Alkaline degradation of the foams was investigated in 10 wt/vol % NaOH at 80°C. The results show that the novel PPO‐b‐PLA copolymers could be promising as degradable polymeric materials. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Mechanical properties and thermal aging behavior of styrene‐butadiene rubbers vulcanized using liquid diene polymers as the plasticizer
Authors: Nakazono Takeo , Matsumoto Akikazu
Published: June 2010

The mechanical properties of styrene‐butadiene rubber (SBR) vulcanizates prepared using various plasticizers including liquid polybutadiene and styrene‐butadiene copolymers were investigated. The effect of the liquid polymers as the plasticizers on the mechanical properties of the polymers, such as the hardness, tensile storage modulus, tanδ, and the modulus at 100% elongation values, were determined before and after the thermal aging. As a result, it was revealed that the use of these liquid polymers gave less amount of change in the measurement values for the mechanical properties during the aging. The crosslinking density and the amount of free polymers were also determined on the basis of the swelling and extraction data, respectively, using several organic solvents. These results support the fact that the added liquid polymers are fixed to the SBR networks. We revealed the superiority of the liquid styrene‐butadiene copolymers as the plasticizer, which provides sufficient mechanical properties after vulcanization and the excellent maintenance of the properties during the thermal aging process. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Effect of polyaniline surface modification of carbon nanofibers on cure kinetics of epoxy resin
Authors: Cai Zhi‐Qi , Movva Siva , Chiou Nan‐Rong , Guerra Dante , Hioe Yunior , Castro Jose M. , Lee L. James
Published: June 2010

Polyaniline (PANI) “nanograss” was grown on carbon nanofibers (CNFs). The cure behavior of an epoxy resin with and without unmodified CNFs or PANI modified CNFs was studied by means of non‐isothermal and isothermal differential scanning calorimetry (DSC). CNFs accelerated the reaction of epoxy and diamine. PANI surface modification further increased the reaction rate and the extent of reaction. An autocatalytic cure kinetic model was used to fit the reaction curves. It was found that activation energies of the epoxy reaction decreased in the presence of CNFs and PANI modified CNFs. The observed catalytic effect of CNF and PANI surface coating can be very useful for low temperature cure of large epoxy composite products. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Latex dispersability index
Authors: Khorassani Manouchehr , Afshar‐Taromi Faramarz , Pourmahdian Saeed
Published: June 2010

The pigment loading capacity (PLC) of dispersion binders is an important factor in the formulation of a latex paint. However, there has been no reliable method for the quantitative evaluation of this property; this has led to difficulty in comparing latex binders in this regard. In this article, a new parameter, the latex dispersability index (LDI), is proposed as a quantitative measure of PLC of latex binders. In this test method, the capability of latex to disperse pigments (or extenders) is quantified on the basis of the idea of the minimum viscosity method for dispersants. The face‐centered cube experimental design was used to synthesize 26 binders. On the basis of this design, the synthesized latexes had a maximum diversity of properties, especially with regard to PLC. The binders were formulated with three mineral powders (i.e., TiO2, CaCO3, and talc). The curves of viscosity versus mass of the resin for all of the samples were prepared. The general trend of the curves was universal and only depended on the nature of the powders. The geometry of the curves and PLC had quantitative correlations. To make a quantitative correlation between the curves and PLC, LDI was defined as a function of the area under the curve, the height of the curve, and the length of the end point. Four ranges of LDI were assigned to the conventional quantitative phrases for PLC. The usefulness of this parameter was then verified by some well‐known commercial binders with different PLCs. The results were in a good agreement with the expected behaviors. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Rheological studies on energetic thermoplastic elastomers
Authors: Reddy T. S. , Nair J. K. , Satpute R. S. , Gore G. M. , Sikder A. K.
Published: June 2010

Energetic thermoplastic elastomers containing energetic groups, such as azido, nitrato, nitro, and so forth, are emerging as attractive binder systems for advanced solid rocket propellants. Poly[3,3‐bis(Azidomethyl) oxetane (BAMO)‐co‐3‐azidomethyl‐3‐methyl oxetane (AMMO)] comprising hard crystalline BAMO segment and the soft/amorphous AMMO segment in various molar ratios (80 : 20, 50 : 50 and 20 : 80) were synthesized during the present work. The homo polymers namely Poly‐BAMO and Poly‐AMMO were also synthesized. All the polymers and copolymers were characterized by spectral and thermal methods. They were found to be thermally stable. The most promising 80 : 20 copolymer softened at 56°C with Tg of −36°C. Rheological studies were also carried out to determine their suitability as a binder in explosive and propellant formulations. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Antibacterial polyvinyl chloride/antibiotic films: The effect of solvent on morphology, antibacterial activity, and release kinetics
Authors: Merchan Martha , Sedlarikova Jana , Sedlarik Vladimir , Machovsky Michal , Svobodova Jitka , Saha Petr
Published: June 2010

Medical‐grade polyvinyl chloride was modified with sodium ampicillin in a concentration range from 0 to 5 wt % by solvent casting technique using cyclohexanone and N,N‐dimethylformamide. The obtained polymeric systems were characterized by optical microscopy, tensile test, and scanning electron microscopy. In addition, in vitro antibacterial activity against Gram‐negative and Gram‐positive bacteria was determined by an agar diffusion test. Antibiotic release experiments were performed in distilled water and physiological saline solution, which were monitored by UV‐vis spectroscopy. The results showed a crucial role of the solvent on the morphology, antibacterial activity, and releasing characteristic of the ampicillin. Furthermore, a mathematical model was applied to data obtained from release study, to characterize the release kinetics of the ampicillin from the polyvinyl chloride‐antibiotic systems. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Synthesis and characterization of poly(ether sulfone)‐graft‐polydimethylsiloxane copolymers
Authors: Chen Zheng , Yang Jinsheng , Guan Shaowei , Li Xiujie , Rong Changru , Jiang Zhenhua
Published: June 2010

Novel poly(arylene ether sulfone) (PAES) polymers containing polydimethylsiloxane (PDMS) side chains were synthesized and characterized with NMR and Fourier transform infrared spectroscopy. The thermal properties of the copolymers were evaluated with differential scanning calorimetry and thermogravimetric analysis. The polymers showed perfect thermal stability, as the decomposition temperatures were all above 380°C, and exhibited glass‐transition temperatures in the range 130–188°C. Furthermore, the surface properties of the copolymers were evaluated by X‐ray photoelectron spectroscopy and contact angle analysis. The results show that the hydrophobic abilities of the graft copolymer surfaces were improved significantly compared to PAES through the introduction of the PDMS chains. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Effect of the particle size and particle agglomeration on composite membrane performance
Authors: García M. G. , Marchese J. , Ochoa N. A.
Published: June 2010

One of the most used methods for studying the rigidification of polymer matrices in composite membranes is differential scanning calorimetry. Glass‐transition temperatures give information about filler–polymer interaction and the rigidity of the polymer matrix. In this study, optical microscopy, mechanical property testing, and X‐ray diffraction, instead of differential scanning calorimetry, were used to study both poly(ether imide) (PEI) matrix rigidification and activated carbon–PEI interfacial adhesion. Then, the permselective properties of the mixed matrix membranes were interpreted. The change in rigidity in these composite membranes was in agreement with the decrease in the flexibility of the composite materials as the filler content increased. This fact was confirmed by the tension and elongation data and X‐ray diffraction (DRX) measurements. However, the Young's modulus value decreased as the carbon content increased. There was an increase in all of the gas permeability coefficients measured in the composites compared with that of PEI. As the particle size grew, a low particle surface area and a poor interfacial adhesion were observed. The carbon agglomerates acted as sites of stress concentration within the polymeric matrix. This decreased the intercatenary distances and limited the movement of polymer chains, which resulted in a more rigid matrix. The higher selectivity of the H2/CH4, H2/CO2 and O2/N2 systems observed in the composite membranes revealed that there were both a preferential sorption of certain gases in the carbon surface or carbon–polymer interface and a molecular size exclusion, which were responsible for that increment, despite the poor interfacial adhesion. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Kinetics of the polymerizable azo initiator 2,2′‐azobis[N‐(2‐propenyl)‐2‐methylpropionamide] and its application to graft copolymerization
Authors: Yasuda Masahiro , Kunieda Hiroshi , Fujiwara Maya , Takenaka Hiroki , Glomm Wilhelm R. , Ogino Hiroyasu , Ishikawa Haruo
Published: June 2010

The polymerizable azo initiator 2,2′‐azobis[N‐(2‐propenyl)‐2‐methylpropionamide] (APMPA) has both vinyl groups and azo groups. To develop a new graft polymerization method, the radical polymerization kinetics of APMPA and graft polymerization with the produced macromolecular azo initiator were studied. Because the azo group of APMPA was stable below 80°C, the vinyl group of APMPA could be polymerized with 2,2′‐azobis(2,4‐dimethylvaleronitrile) as an initiator at 60 and 70°C. However, the homopolymerization of APMPA could not proceed because of APMPA self‐circulation reactions. Using comonomers such as styrene (ST), methyl methacrylate (MMA), and vinyl acetate, we synthesized copolymers of APMPA. The 1H‐NMR spectra of the resulting copolymers showed the incorporation of APMPA. With the copolymer composed of ST and APMPA used as an initiator, the gel permeation chromatogram showed that the high‐molecular‐mass fraction of the grafted polymer increased with time. By this method, grafted copolymers having branched chains composed of ST, MMA, or an amphiphilic macromonomer were obtained. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Processing characteristics of low‐density polyethylene filled with calcium carbonate of different size distributions
Authors: Zhang Jun , Fang Jue , Wu Jun‐Li , Wu Juan , Zhou Ning‐Lin , Mo Hong , Ma Zhen‐Mao , Shen Jian
Published: June 2010

Low‐density polyethylene (LDPE) was filled with blends of different proportions of two sizes of calcium carbonate (CaCO3; 600 and 2500 mesh). The torque of the LDPE/CaCO3 samples was measured with a torque rheometer. The results showed that the process torque values of the LDPE/CaCO3 samples obviously decreased when LDPE was filled with a blend of two sizes of CaCO3 (600‐ and 2500‐mesh CaCO3 blend) in comparison with samples filled with CaCO3 of a single size (600 or 2500 mesh). When the ratio of 600‐mesh CaCO3 to the total CaCO3 was in the range of 40–60 wt %, the lowest torque value of the LDPE/CaCO3 samples was achieved. When the content of CaCO3 in a sample was 30 wt %, LDPE filled with CaCO3 of different size distributions showed the largest decrease in the torque ratio in comparison with the samples filled with CaCO3 of a single size. The torques of LDPE samples filled with CaCO3 of a single size and those filled with CaCO3 of different size distributions at different temperatures were also studied. The results showed that the flow activation energy and flow activation entropy of LDPE samples filled with CaCO3 of different size distributions increased obviously. The increase in the flow activation entropy was used to explain the phenomenon of the process torque decreasing for LDPE samples filled with CaCO3 of different size distributions. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Synthesis and characterization of poly(ether‐block‐amide) and application as permanent antistatic agent
Authors: Wang Guojian , Xue Bing
Published: June 2010

Poly(ether‐block‐amide) (PEBA) were prepared by means of a condensation reaction with polyamide‐6 as hard segment and polyether as soft segment. The optimal reaction conditions were determined as the followings: 3% of water and 0.35% of catalyst, reaction temperature 260°C ± 5°C and the reaction time 4 h under the N2 atmosphere, and 1 h under the vacuum, the vacuum <80 Pa. Characterization results of FTIR and 1H‐NMR showed that the block copolymer of polyether and polyamide was synthesized successfully. The obtained PEBA was applied as an antistatic agent for the ABS resin. The research results showed that the blend with the best properties was PEBA2‐2/ABS and the dosage of PEBA was 12%. PEBA2‐2 could obviously decrease the surface resistivity of ABS from 1014 to 1010Ω and also exhibit good persistent antistatic ability. The surface resistivity of the blends decreased with the increase of content of PEBA. The increase of ratio of polyether in PEBA was favorable for the decrease of surface resistivity of the blends. The observation of SEM indicated that the PEBA and ABS had good compatibility. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Cellulose acetate/multiwalled carbon nanotube nanocomposites with improved mechanical, thermal, and electrical properties
Authors: Li Meilu , Kim Il‐Hwan , Jeong Young Gyu
Published: June 2010

Cellulose acetate (CA)‐based nanocomposites with various contents of neat multiwalled carbon nanotube (MWCNT) or acid‐treated one (MWCNT‐COOH) are prepared via melt‐compounding method and investigated their morphology, thermal stability, mechanical, and electrical properties. SEM microphotographs reveal that MWCNT‐COOHs are dispersed uniformly in the CA matrix, compared with neat MWCNTs. FTIR spectra support that there exists a specific interaction between carboxyl groups of MWCNT‐COOHs and ester groups of CA, indicating good interfacial adhesion between MWCNT‐COOHs and CA matrix. Accordingly, thermal stability and dynamic mechanical properties of CA/MWCNT‐COOH nanocomposites were higher than those of CA/MWCNT composites. On the contrary, electrical volume resistivities of CA/MWCNT‐COOH nanocomposites are found to be somewhat higher than those of CA/MWCNT composites, which is because of the deterioration of graphene structures for MWCNT‐COOHs and the good dispersion of MWCNT‐COOHs in the CA matrix. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Good properties of similarity measures and their complementarity
Authors: Egghe Leo
Published: June 2010

Similarity measures, such as the ones of Jaccard, Dice, or Cosine, measure the similarity between two vectors. A good property for similarity measures would be that, if we add a constant vector to both vectors, then the similarity must increase. We show that Dice and Jaccard satisfy this property while Cosine and both overlap measures do not. Adding a constant vector is called, in Lorenz concentration theory, “nominal increase” and we show that the stronger “transfer principle” is not a required good property for similarity measures. Another good property is that, when we have two vectors and if we add one of these vectors to both vectors, then the similarity must increase. Now Dice, Jaccard, Cosine, and one of the overlap measures satisfy this property, while the other overlap measure does not. Also a variant of this latter property is studied.
Heterogeneous Aromatic Amination of Aryl Halides with Arylamines in Water with PS‐PEG Resin‐Supported Palladium Complexes
Authors: Hirai Yoshinori , Uozumi Yasuhiro
Published: June 2010

Catalytic aromatic amination is achieved in water under heterogeneous conditions by the use of immobilized palladium complexes coordinated with the amphiphilic polystyrene‐poly(ethylene glycol) resin‐supported di(tert‐butyl)phosphine ligand. Aromatic amination of aryl halides with diphenylamine and N,N‐double arylation of anilines with bromobenzene were found to proceed in water with broad substrate tolerance to give the triarylamines in high yield with high recyclability of the polymeric catalyst beads. Very little palladium leached from the polymeric catalyst under the water‐based reaction conditions to provide a green and clean (metal‐uncontaminated) protocol for the preparation of triarylamines, including the optoelectronically active N,N,N′,N′‐tetraaryl‐1,1′‐biphenyl‐4,4′‐diamines (TPDs).
Identification based adaptive iterative learning controller
Authors: Ashraf Suhail , Muhammad Ejaz , Al‐Habaibeh Amin
Published: June 2010

In recent years, more research in the control field has been in the area of self‐learning and adaptable systems, such as a robot that can teach itself to improve its performance. One of the more promising algorithms for self‐learning control systems is Iterative Learning Control (ILC), which is an algorithm capable of tracking a desired trajectory within a specified error limit. Conventional ILC algorithms have the problem of relatively slow convergence rate and adaptability. This paper suggests a novel approach by combining system identification techniques with the proposed ILC approach to overcome the aforementioned problems. The ensuing design procedure is explained and results are accrued from a number of simulation examples. A key point in the proposed scheme is the computation of gain matrices using the steepest descent approach. It has been found that the learning rule can be guaranteed to converge if certain conditions are satisfied.

Copyright © 2010 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society
Disturbance decoupled fault reconstruction using sliding mode observers
Authors: Ng Kok Yew , Tan Chee Pin , Akmeliawati Rini , Edwards Christopher
Published: June 2010

This paper investigates and presents conditions that guarantee disturbance decoupled fault reconstruction using sliding mode observers, which are less stringent than those of previous work, and show that disturbance reconstruction is not necessary. An aircraft model validates the ideas proposed in this paper.

Copyright © 2010 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society