bluuebunny/crossref_metadata_2025 huggingface dataset:
SOME ITERATIVE REGULARIZED METHODS FOR HIGHLY NONLINEAR LEAST SQUARES PROBLEMS
Authors: Kangro Inga , Vaarmann Otu
Published: May 2009

This report treats numerical methods for highly nonlinear least squares problems for which procedural and rounding errors are unavoidable, e.g. those arising in the development of various nonlinear system identification techniques based on input‐output representation of the model such as training of artificial neural networks. Let F be a Frechet‐differentiable operator acting between Hilbert spaces H1 and H2 and such that the range of its first derivative is not necessarily closed. For solving the equation F(x) = 0 or minimizing the functional f(x) = ½ ‖F(x)‖2 , x H 1, two‐parameter iterative regularization methods based on the Gauss‐Newton method under certain condition on a test function and the required solution are developed, their computational aspects are discussed and a local convergence theorem is proved.
CONSERVATIVE NUMERICAL METHOD FOR A SYSTEM OF SEMILINEAR SINGULARLY PERTURBED PARABOLIC REACTION‐DIFFUSION EQUATIONS
Authors: Shishkina Lidia , Shishkin Grigorii
Published: May 2009

On a vertical strip, a Dirichlet problem is considered for a system of two semilinear singularly perturbed parabolic reaction‐diffusion equations connected only by terms that do not involve derivatives. The highest‐order derivatives in the equations, having divergent form, are multiplied by the perturbation parameter e ; ϵ ∈ (0,1]. When ϵ → 0, the parabolic boundary layer appears in a neighbourhood of the strip boundary. Using the integro‐interpolational method, conservative nonlinear and linearized finite difference schemes are constructed on piecewise‐uniform meshes in the x 1 ‐axis (orthogonal to the boundary) whose solutions converge ϵ‐uniformly at the rate O (N1−2 ln2 N 1 + N 2 −2 + N 0 −1). Here N 1 + 1 and N 0 + 1 denote the number of nodes on the x 1‐axis and t‐axis, respectively, and N 2 + 1 is the number of nodes in the x 2‐axis on per unit length.
MULTIDIMENSIONAL SCALING WITH CITY‐BLOCK DISTANCES BASED ON COMBINATORIAL OPTIMIZATION AND SYSTEMS OF LINEAR EQUATIONS
Authors: Žilinskas Julius
Published: May 2009

Multidimensional scaling is a technique for exploratory analysis of multidimensional data. The essential part of the technique is minimization of a multimodal function with unfavorable properties like invariants and non‐differentiability. In this paper a two‐level optimization based on combinatorial optimization and systems of linear equations is proposed exploiting piecewise quadratic structure of the objective function with city‐block distances. The approach is tested experimentally and improvement directions are identified.
Genetic differentiation of Atlantic populations of the intertidal copepod Tigriopus brevicornis
Authors: Denis Françoise , Ravallec Rozenn , Pavillon Jean-François , Van Wormhoudt Alain
Published: May 2009

The Harpacticoid copepod Tigriopus brevicornis belongs to the meiofauna of intertidal rock pools and is distributed widely along European coasts. Sixteen sites were sampled from the Irish Sea to the coasts of Spain. We used the ITS1 marker to analyse the relationship between the populations because it shows low intrapopulational variation (mean pairwise difference: 1.00 ± 0.8) and high interpopulational divergence (mean pairwise difference: 16.38 ± 7.39). A total of 57 bp out of 433 bp were recognised as informative nucleotides among the 61 individuals analysed. The analysis of the genetic relationships highlighted a north-south split in the distribution of the natural populations and showed a genetic break point around the Gironde estuary, which is probably due to differences in the geomorphologic characteristics of the coastal area on the two different sides of this estuary. Various populations were isolated and the ITS1 sequences indicated that there are specific genetic signatures in these populations. The northern set of populations, which was sampled along a large rocky coastline, had a metapopulation structure with genetic exchanges between geographically close populations and also between geographically far ones. The southern set of populations, which was sampled in small rocky pools on large sandy beaches, showed isolated populations as a consequence of the geomorphology of the area.
Case study of a one‐sided attack by multiple troop members on a nontroop adolescent male and the death of Japanese macaques (Macaca fuscata)
Authors: Shimada Masaki , Uno Takeharu , Nakagawa Naofumi , Fujita Shiho , Izawa Kosei
Published: May 2009

An adolescent wild male Japanese macaque (Macaca fuscata), following Kinkazan A troop, was attacked one‐sidedly by multiple members of the troop. The victim was identified as PI, and was estimated to be seven±one year old. The aggressive interaction was recorded by video camera until the end. Although at least 16 troop members approached PI more than once, only three males (one adult, two adolescents) of A troop attacked him. PI kept crouching throughout the attack, then escaped to the shore and dived into the sea. The interaction continued for more than one hour. PI was found dead a few hours after the end of interaction. The damage caused by the assailants was not the direct cause of PI's death; it was due to hypothermia caused by drifting in the sea. PI's life history was reconstructed from past records. PI was a normal adolescent male who migrated from an all‐male group around B1 troop and started ranging around A troop. The aggressive interaction is believed to be a typical example of conflict between troop males and a nontroop male. The interaction period was very long compared with previous reports on such conflicts among Japanese macaques. PI kept crouching in open areas, exposing himself as a potential competitor for the resources of the troop, and did not show any submissive or reconciliatory behavior toward the troop males. This may be why the troop males did not stop the attack. Aggr. Behav. 35:334–341, 2009. © 2009 Wiley‐Liss, Inc.
Kinetic modeling of catalytic conversion of methylcyclohexane over USY zeolites: Adsorption and reaction phenomena
Authors: Al‐Sabawi Mustafa , de Lasa Hugo
Published: May 2009

Catalytic conversion of cycloparaffins is a complex process involving competing reaction steps. To understand this process, FCC experiments using methylcyclohexane (MCH) on USY zeolite catalysts were carried out in the mini‐fluidized CREC riser simulator. Runs were developed under relevant FCC process conditions in terms of partial pressures of MCH, temperatures (450–550°C), contact times (3–7 s), catalyst‐oil mass ratios (5), and using fluidized catalysts. MCH overall conversions ranged between 4 to 16 wt %, with slightly higher conversions obtained using the larger zeolite crystallites. Moreover, it was found that MCH undergoes ring opening, protolytic cracking, isomerization, hydrogen transfer and transalkylation. A heterogeneous kinetic model for MCH conversion including thermal effects, adsorption and intrinsic catalytic reaction phenomena was established. Adsorption and kinetic parameters were determined, including the heat of adsorption (−40 kJ/mol), as well as thermal and primary catalytic intrinsic activation energies, which were in the range of 43–69 kJ/mol, and 50–74 kJ/mol, respectively. © 2009 American Institute of Chemical Engineers AIChE J, 2009
Erste Röntgenstrukturanalysen von Rhodium(III)‐η1‐Allyl‐Komplexen und ein plausibler Mechanismus für allylische Isomerisierungsreaktionen
Authors: Wucher Barbara , Moser Michael , Schumacher Stephanie A. , Rominger Frank , Kunz Doris
Published: May 2009

Allyltransfer von Metall zu Metall: Anhand der ersten strukturell charakterisierten Rh(η1‐allyl)‐Komplexe wird gezeigt, dass der σ‐gebundene Allylsubstituent von einem RhIII‐ auf einen RhI‐Komplex im schnellen Gleichgewicht übertragen werden kann. Dies könnte die Abnahme der Regioselektivität in Rh‐katalysierten allylischen Alkylierungen erklären, für die Komplex 1 ein aktiver Katalysator ist.

magnified image
Surprisingly Long‐Range Surface‐Enhanced Raman Scattering (SERS) on Au–Ni Multisegmented Nanowires
Authors: Wei Wei , Li Shuzhou , Millstone Jill E. , Banholzer Matthew J. , Chen Xiaodong , Xu Xiaoyang , Schatz George C. , Mirkin Chad A.
Published: May 2009

Erstaunlich weitreichend ist die oberflächenverstärkte Raman‐Streuung an einem Nickelnanodraht, der sich in 120 nm Entfernung von zwei Goldnanoscheiben befindet. Die Anregung der Oberflächenplasmonenresonanz (SPR) im Nanoscheibenpaar erhöht das elektromagnetische Feld nahe dem Nickelsegment (SEM, links), was zu einer erhöhten Raman‐Intensität führt (rechts).

magnified image
Palladiumkatalysierte Carbonylierungen von Arylhalogeniden und ähnlichen Substraten
Authors: Brennführer Anne , Neumann Helfried , Beller Matthias
Published: May 2009

Um eine CO‐Gruppe reicher: (Hetero‐)Arene sind aus der industriellen Herstellung von Agrochemikalien, Farbstoffen, Pharmaka etc. nicht wegzudenken. Während der vergangenen Jahrzehnte wurden übergangsmetallkatalysierte Kupplungen von Arylhalogeniden mit Nucleophilen aller Art entwickelt. Dieser Aufsatz fasst aktuelle Fortschritte auf dem Gebiet der palladiumkatalysierten Carbonylierungen von Arylhalogeniden und ähnlichen Verbindungen zusammen (siehe Schema).

magnified image

Palladiumkatalysierte Carbonylierungen von Arylhalogeniden in Gegenwart verschiedener Nucleophile haben sich seit ihrer Einführung durch Heck und Mitarbeiter im Jahr 1974 schnell weiterentwickelt, sodass heute eine Vielzahl von Palladiumkatalysatoren für unterschiedliche Carbonylierungsreaktionen verfügbar ist. Auf diesem Weg erhältliche Carbonsäurederivate, Aldehyde und Ketone sind wichtige Zwischenstufen bei der industriellen Herstellung von Farbstoffen, Pharmaka, Agrochemikalien und anderen Produkten. In diesem Aufsatz werden aktuelle Ergebnisse aus der akademischen Forschung und erste industrielle Prozesse zusammengefasst.
Fluorescence Detection of Single‐Nucleotide Polymorphisms with a Single, Self‐Complementary, Triple‐Stem DNA Probe
Authors: Xiao Yi , Plakos Kory J. I. , Lou Xinhui , White Ryan J. , Qian Jiangrong , Plaxco Kevin W. , Soh H. Tom
Published: May 2009

Eine Abweichung genügt: Bei einer einstufigen, nur eine Komponente nutzenden, fluoreszenzbasierten Methode zum Nachweis von Einzelnucleotidpolymorphismen bei Raumtemperatur besteht der Sensor aus einem einzigen, selbstkomplementären DNA‐Strang, der eine Dreifachstammstruktur bildet. Die große Konformationsänderung beim Binden an perfekt komplementäre (PM‐)Ziele führt zu einer deutlichen Zunahme der Fluoreszenz (siehe Bild; F=Fluorophor, Q=Quencher).

magnified image
A p‐Type NiO‐Based Dye‐Sensitized Solar Cell with an Open‐Circuit Voltage of 0.35 V
Authors: Gibson Elizabeth A. , Smeigh Amanda L. , Le Pleux Loïc , Fortage Jérôme , Boschloo Gerrit , Blart Errol , Pellegrin Yann , Odobel Fabrice , Hagfeldt Anders , Hammarström Leif
Published: May 2009

Starkes Tandem: Eine molekulare Diade und ein cobalthaltiger Elektrolyt sorgen für eine Verdreifachung der Leerlaufspannung (VOC) in einer p‐NiO‐Zelle (VOC= 0.35 V) und eine viermal effizientere Energieumwandlung. Eine farbstoffsensibilisierte TiO2/NiO‐Tandemsolarzelle mit diesem verbesserten System brachte es auf VOC=0.91 V (siehe Bild; LB=Leitungsband, VB=Valenzband).

magnified image
Das ungeradzahlig elektronenkonfigurierte Komplexion [Ruk(NOm)(Qn)(terpy)]2+ mit zwei idealtypischen “nicht‐unschuldigen” Liganden
Authors: Das Atanu Kumar , Sarkar Biprajit , Duboc Carole , Strobel Sabine , Fiedler Jan , Záliš Stanislav , Lahiri Goutam Kumar , Kaim Wolfgang
Published: May 2009

Sechs Kombinationen von Oxidationszuständen stehen der paramagnetischen Titelverbindung zur Auswahl. Kristallographische, computergestützte (DFT) und spektroskopische Studien (EPR bei konventionellen und hohen Frequenzen, IR) sprechen für die Iminosemichinon‐Form mit k=2+, m=1+ und n=1−.

magnified image
Funktionalisierte Template für den konvergenten Aufbau von Polyethern: Synthese der HIJK‐Ringe von Gymnocin A
Authors: Van Dyke Aaron R. , Jamison Timothy F.
Published: May 2009

Leiterverlängerung: Der Erfolg einer Epoxidöffnungsstrategie zur Synthese leiterförmiger Polyether hängt davon ab, ob die entstehenden Produkte weiter umgesetzt werden können. Mithilfe zweier funktionalisierter Template wurde ein Fragment von Gymnocin A synthetisiert, das vier differenzierte Stellen für die darauffolgende Fragmentkupplung enthält (siehe Schema; Bn=Benzyl).

magnified image
Enantioselective Addition of Boronates to Acyl Imines Catalyzed by Chiral Biphenols
Authors: Bishop Joshua A. , Lou Sha , Schaus Scott E.
Published: May 2009

Schnell gefunden: Ein Screening chiraler Biphenolkatalysatoren ermöglichte die rasche Identifizierung enantioselektiver nucleophiler Reaktionen von Boronaten mit Acyliminen (siehe Schema). Damit konnte ein einzigartiger Katalysator für die Reaktion von Aryl‐, Vinyl‐ und Alkinylboronaten gefunden werden. Mechanistische Studien ergaben, dass ein Ligandenaustausch zwischen Boronat und Katalysator für die Aktivierung notwendig ist.

magnified image
Molekulare Stäbe mit Oligospiroketal‐Rückgrat als Anker in Biomembranen
Authors: Müller Peter , Nikolaus Jörg , Schiller Sabine , Herrmann Andreas , Möllnitz Kristian , Czapla Sylvia , Wessig Pablo
Published: May 2009

Anker im Nanomaß‐Stab: Ein hydrophober molekularer Stab mit terminalen fluoreszierenden Gruppen wurde synthetisiert und ließ sich effizient in Modellmembranen und biologische Membranen einbauen (siehe Bild; grau C, blau N, rot O). Derartige Stäbe können als stabile membranassoziierte Anker für die Funktionalisierung von Membranoberflächen eingesetzt werden.

magnified image
Oxygen Electroreduction Catalyzed by Gold Nanoclusters: Strong Core Size Effects
Authors: Chen Wei , Chen Shaowei
Published: May 2009

Größer heißt nicht besser: Gold‐Nanocluster zeigten eine erhöhte elektrokatalytische Aktivität in der Sauerstoffreduktion, wenn der Partikelkern von Au140 auf Au11 verkleinert wurde (siehe Auftragung des Onset‐Potentials Eonset und der Spitzenstromdichte JK). Der zunehmende Anteil an Oberflächenatomen und die Verschiebung des d‐Elektronenbands zum Fermi‐Niveau erleichtern die Sauerstoffadsorption.

magnified image
Fast Attrition‐Enhanced Deracemization of Naproxen by a Gradual In Situ Feed
Authors: Noorduin Wim L. , Kaptein Bernard , Meekes Hugo , van Enckevort Willem J. P. , Kellogg Richard M. , Vlieg Elias
Published: May 2009

Mahlen heilt: Mithilfe des nichtsteroidalen Entzündungshemmers Naproxen ist es möglich, die Geschwindigkeit der kürzlich entdeckten Deracemisierung durch abrasives Vermahlen enorm zu erhöhen. Das Verfahren nutzt ein kontinuierliches Einspeisen des racemischen Zielmaterials durch In‐situ‐Umwandlung.

magnified image
Palladium‐Catalyzed Carbonylation Reactions of Aryl Halides and Related Compounds
Authors: Brennführer Anne , Neumann Helfried , Beller Matthias
Published: May 2009

A CO group richer: (Hetero)arenes are vital intermediates in the manufacture of agrochemicals, dyes, pharmaceuticals, and other industrial products. In the past decades transition‐metal‐catalyzed coupling reactions of aryl halides with all types of nucleophiles have been developed. This Review summarizes recent work in the area of palladium‐catalyzed carbonylation reactions of aryl halides and related compounds (see scheme).

magnified image

Palladium‐catalyzed carbonylation reactions of aromatic halides in the presence of various nucleophiles have undergone rapid development since the pioneering work of Heck and co‐workers in 1974, such that nowadays a plethora of palladium catalysts are available for different carbonylative transformations. The carboxylic acid derivatives, aldehydes, and ketones prepared in this way are important intermediates in the manufacture of dyes, pharmaceuticals, agrochemicals, and other industrial products. In this Review, the recent academic developments in this area and the first industrial processes are summarized.
Fluorescence Detection of Single‐Nucleotide Polymorphisms with a Single, Self‐Complementary, Triple‐Stem DNA Probe
Authors: Xiao Yi , Plakos Kory J. I. , Lou Xinhui , White Ryan J. , Qian Jiangrong , Plaxco Kevin W. , Soh H. Tom
Published: May 2009

Singled out for its singularity: In a single‐step, single‐component, fluorescence‐based method for the detection of single‐nucleotide polymorphisms at room temperature, the sensor is comprised of a single, self‐complementary DNA strand that forms a triple‐stem structure. The large conformational change that occurs upon binding to perfectly matched (PM) targets results in a significant increase in fluorescence (see picture; F=fluorophore, Q=quencher).

magnified image
Enantioselective Addition of Boronates to Acyl Imines Catalyzed by Chiral Biphenols
Authors: Bishop Joshua A. , Lou Sha , Schaus Scott E.
Published: May 2009

On the big screen: A chiral biphenol catalyst screening protocol was developed for the rapid identification of enantioselective nucleophilic boronate reactions with acyl imines (see scheme). The approach successfully identified a unique catalyst for the reaction of aryl, vinyl, and alkynyl boronates. Mechanistic studies demonstrate boronate ligand exchange with the catalyst is necessary for activation towards nucleophilic addition.

magnified image
Oxygen Electroreduction Catalyzed by Gold Nanoclusters: Strong Core Size Effects
Authors: Chen Wei , Chen Shaowei
Published: May 2009

Bigger isn't better: Gold nanoclusters exhibit enhanced electrocatalytic activity in oxygen reduction when the core size decreased from Au140 to Au11, as reflected by the onset potential Eonset and peak current density JK (see picture). The increasing fraction of surface atoms with low coordination numbers and the shift of the d‐band center to the Fermi level facilitate oxygen adsorption.

magnified image
Fast Attrition‐Enhanced Deracemization of Naproxen by a Gradual In Situ Feed
Authors: Noorduin Wim L. , Kaptein Bernard , Meekes Hugo , van Enckevort Willem J. P. , Kellogg Richard M. , Vlieg Elias
Published: May 2009

Grind and cure: Using the nonsteroidal anti‐inflammatory drug naproxen, a novel concept is demonstrated to dramatically enhance the rate of the recently discovered process of deracemization using abrasive grinding. The process relies on a gradual feed of the racemic target material by an in situ conversion.

magnified image
Synthesis and application of water‐soluble hyperbranched poly(ester)s from maleic anhydride and glycerol
Authors: Zhao Xiaofei , Liu Lixin , Dai Hongxia , Ma Chunxi , Tan Xiaohong , Yu Rihua
Published: May 2009

A water‐soluble hyperbranched polyester with a considerable number of hydroxyl terminal groups was synthesized by reacting maleic anhydride and glycerol in the absence of a solvent. The synthesized intermediate product was converted to the hyperbranched polyester by condensation polymerization, and the water by‐product produced during the esterification reaction may be removed by vacuum distillation. In the synthesis process, the crosslinking reaction occurs readily if maleic anhydride is in excess. The result shows that the product synthesized by this one‐step method is insoluble in water at room temperature, whereas the product of a quasi one‐step method, in which pentaerythritol was added as a core molecule, has good water solubility when pentaerythritol and the raw material have a molar ratio of 1 : 100 or 1 : 150. The resulting hyperbranched polyester was purified by column chromatography and characterized by infrared spectrometry. The synthetic hyperbranched polyester was used at 0.5% as a crosslinking agent for acrylic ester to inform acrylic ester latex film; the water absorption of the film was decreased significantly, the viscosity was increased, and some mechanical properties were improved. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Synthesis and rheological behavior of a novel N‐sulfonate ampholyte chitosan
Authors: Yin Qiang , Li Yan , Yin Qin‐Jian , Miao Xia , Jiang Bo
Published: May 2009

Modified chitosan derivatives with different degrees of substitution varying from 0.17 to 0.96 were synthesized by the heterogeneous reaction of chitosan with 3‐chloro‐2‐hydroxy propanesulfate in a neutral aqueous solution. The modified chitosans with a degree of substitution higher than 0.36 were soluble in water, whatsoever the pH. The structures of the polymers were characterized by Fourier transform infrared and 1H‐nuclear magnetic resonance spectroscopies. The potentiometric titration revealed that the modified chitosan had an isoelectric point at around pH = 5.7, and its rheological behaviors in aqueous solution were studied under different conditions. The results showed that the modified chitosan had typical polyampholyte characteristics, which exhibited polyelectrolyte effect at pH = 1.7 or 13 and antipolyelectrolyte effect at pH = 8. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Tensile performance and crack propagation of coated woven fabrics under multiaxial loads
Authors: Chen Shouhui , Ding Xin , Fangueiro Raul , Yi Honglei , Yang XuDong
Published: May 2009

The tensile performance of coated woven fabrics under multiaxial loads is examined in the present study. Two groups of experiments were conducted to investigate the influences of the configuration of the fabric specimen and the loading speed on the multiaxial tensile properties of the fabrics. The configuration of the specimen for the multiaxial tensile tests is identified as gear‐shape with large arm widths. A loading speed of lower than 20 mm/min is suggested to obtain the tensile properties of the coated woven fabrics under multiaxial loads. The tensile performances of coated woven fabrics under uni‐, bi‐, and multiaxial loads were compared. We found that the tensile performances under bi‐ and multiaxial loads are much better than those under uniaxial loads. Therefore, for the application of the coated woven fabrics in lightweight structures, biaxial or multiaxial loading conditions will be necessary. Experiments on the specimens with an initial crack in the center under multiaxial loads show that, by comparison with other loading directions, the tensile properties in warp direction of the coated woven fabrics play an important role in the failure performance and crack propagation under multiaxial loads. To eliminate the dependence on the mechanical properties in warp direction, the balance of the two principle directions of coated woven fabrics should be improved. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Novel aluminum phosphate/cyanate ester composites: Thermodegradation behaviors and kinetic analyses
Authors: Sun Zhouqiang , Gu Aijuan , Liang Guozheng , Dai Shankai , Yuan Li
Published: May 2009

Thermodegradation behaviors of novel aluminum phosphate/cyanate ester (AlPO4(KH550)/CE) composites were studied in detail. Results show that thermodegradation behaviors and kinetic parameters of AlPO4(KH550)/CE composites are greatly dependent on the AlPO4(KH550) loading. The addition of AlPO4(KH550) into CE resin changes the thermodegradation mechanism (mainly at the temperature lower than 450°C) and degradation process from two steps to three steps. Comparing with CE resin, AlPO4(KH550)/CE composites have lower initial degradation temperature and greatly higher char yield. Besides, for each thermodegradation step, the more the AlPO4 content, the smaller the activation energy value is. All reasons leading to these outcomes are investigated intensively. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Influence of high temperature and pressure ammonia solution treatment on interfacial behavior of carbon fiber/epoxy resin composites
Authors: Meng L. H. , Chen Z. W. , Song X. L. , Liang Y. X. , Huang Y. D. , Jiang Z. X.
Published: May 2009

The method of high temperature and pressure ammonia solution treatment to improve the interfacial performances of carbon fiber/epoxy composites is discussed in this study. Besides, the influence of high temperature and pressure ammonia solution treatment on carbon fiber and its reinforced epoxy composite interface performance were studied. The untreated and treated carbon fibers were characterized by monofilament tensile test, X‐ray photoelectron spectroscopy (XPS), and atomic force microscope (AFM). The interfacial adhesion of the untreated and treated carbon fibers reinforced epoxy resin composites were also evaluated by interface shear strength (IFSS) test, interlaminar shear strength (ILSS) test, and fracture morphology analysis. It was found that the interfacial adhesion of composites increased greatly after high temperature and pressure ammonia solution treatment. The improvement of interfacial adhesion was attributed to the increase of polar functional groups and surface roughness of carbon fibers surface after treatment. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Chemically modified sugarcane bagasse as an improving agent for the properties of styrene–butadiene rubber
Authors: Abdelwahab N. A. , Helaly F. M.
Published: May 2009

The agrowaste of sugarcane bagasse was used as a filler to improve the properties of rubber. Sugarcane bagasse waste was ground and sieved to a particle size less than 75 nm and then purified and chemically modified by an acetylation method and stearic acid adsorption. The modified bagasse was incorporated into styrene–butadiene rubber formulations with different concentrations (20, 30, 50, and 70 phr) in comparison with carbon black and hisil, commercial fillers used in industry. The physicomechanical properties of the rubber vulcanizates were determined before and after thermal aging at 90°C. The retained values of the tensile strength, elongation at break, and equilibrium swelling increased as the concentration of the modified bagasse increased in styrene–butadiene rubber vulcanizates until 50 phr; after this concentration, the retained values of each property decreased. Rubber vulcanizates containing modified bagasse with a concentration of 50 phr may be better for retained values of the physicomechanical properties and equilibrium swelling in comparison with those containing carbon black, hisil, and untreated bagasse. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Aminofunctionalization effect on the microtribological behavior of carbon nanotube/bismaleimide nanocomposites
Authors: Liu Lina , Fang Zhengping , Gu Aijuan , Guo Zhenghong
Published: May 2009

Original multiwalled carbon nanotubes (O‐MWCNTs) and aminofunctionalized ethylenediamine‐treated multiwalled carbon nanotubes (MWCNTs‐EDA) were mixed with bismaleimide (BMI) resin to prepare O‐MWCNT/BMI and MWCNT‐EDA/BMI composites, respectively. Raman spectroscopy, thermogravimetric analysis, and infrared spectroscopy were used to investigate the influence of aminofunctionalization on the multiwalled carbon nanotube (MWCNT) framework. Dynamic mechanical analysis, scanning electron microscopy images of the fractured surface, and field emission scanning electron microscopy of the worn surface were used to determine the possible friction and wear mechanisms of the system. The MWCNT‐EDA/BMI composite exhibited a higher friction coefficient value and a lower wear loss rate value than the O‐MWCNT/BMI composite, which was attributed to the larger number of defects caused by the aminofunctionalization of the MWCNTs, the stronger interfacial adhesion formed between the MWCNTs‐EDA and the BMI resin, and the better dispersive state of the MWCNTs‐EDA in the BMI matrix. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
The characteristics of carbon nanotube‐reinforced poly(phenylene sulfide) nanocomposites
Authors: Yu Suzhu , Wong Wai Mun , Hu Xiao , Juay Yang Kay
Published: May 2009

Multiwall carbon nanotube reinforced poly (phenylene sulfide) (PPS) nanocomposites were successfully fabricated through melt compounding. Structural, electrical, thermal, rheological, and mechanical properties of the nanocomposites were systematically studied as a function of carbon nanotube (CNT) fraction. Electrical conductivity of the polymer was dramatically enhanced at low loading level of the nanotubes; the electrical percolation threshold lay between 1 and 2 wt % of the CNTs. Rheological properties of the PPS nanocomposites also showed a sudden change with the CNT fraction; the percolation threshold was in the range of 0–0.5 wt % of CNTs. The difference in electrical and rheological percolation threshold was mainly due to the different requirements needed in the carbon nanotube network in different stages. The crystallization and melting behavior of CNT‐filled PPS nanocomposites were studied with differential scanning calorimetry; no new crystalline form of PPS was observed in the nanocomposites, but the crystallization rate was reduced. The thermal and mechanical properties of the nanocomposites were also investigated, and both of them showed significant increase with CNT fraction. For 5 wt % of CNT‐filled PPS composite, the onset of degradation temperature increased by about 13.5°C, the modulus increased by about 33%, and tensile strength increased by about 172%. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Study on the optical properties of sulfur‐containing poly(methyl methacrylate)‐inorganic hybrid
Authors: Liu Shujuan , Tian Liying , Zheng Zhen , Wang Xinling
Published: May 2009

High refractive index homogeneous hybrid materials were successfully prepared. The polymer matrix was the copolymer of methyl methacrylate, sulfur‐containing monomer 2,2′‐mercaptoethylsulfide dimethacrylate (MESDMA), and nanotitania was prepared by in situ solgel process of titanium n‐butoxide. The transmission electron microscope (TEM) study suggested that the hybrid was homogeneous without inorganic agglomerate, and the inorganic particles were 4–7 nm. The refractive index was ∼ 1.75 when the inorganic content of the hybrid film reached to 70 wt %, and the transmittance maintained up to 85%. The sulfur‐containing monomer was used to improve the refractive index, also, it was a crosslinking reagent, which improved the film‐forming ability of the hybrid. After copolymerized with MESDMA, the film‐forming ability of the hybrid was better than the one without MESDMA. Even if the inorganic content exceeded 75 wt %, the films kept integrity. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Synergistic effect of halide ions and polyethylene glycol on the corrosion inhibition of aluminium in alkaline medium
Authors: Umoren S.A. , Ebenso E.E. , Ogbobe O.
Published: May 2009

The corrosion inhibition of aluminium in alkaline medium was studied at 30 and 40°C in the presence of polyethylene glycol (PEG) using gravimetric (weight loss) and thermometric techniques. The effect of halides (KCl, KBr, and KI) on the inhibitory action of PEG was also studied. It was found that PEG acted as inhibitor for aluminium corrosion in the alkaline medium. Inhibition efficiency increased with increasing inhibitor concentration. An increase in temperature led to increase in both the corrosion rate and inhibition efficiency in the absence and presence of inhibitor and halides. Phenomenon of chemical adsorption mechanism is proposed from the values of Ea, Qads, and ΔG obtained. The adsorption of PEG on the surface of aluminium was found to obey Flory–Huggins and Temkin adsorption isotherms. The synergism parameter, S1 evaluated was found to be greater than unity indicating that the enhanced inhibition efficiency caused by the addition of halides is synergistic in nature. The inhibition efficiency, surface coverage and synergism parameter increased in the order; I−> Br−> Cl− showing that a joint adsorption of PEG and halide ions on aluminium plays a significant role in the adsorption process. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Synthesis and characterization of copolymers of poly(ethylene terephthalate) and cyclohexane dimethanol in a semibatch reactor (including the process model)
Authors: Sepehri Sanam , Rafizadeh Mehdi , Afshar‐Taromi Framarz
Published: May 2009

Although poly(ethylene terephthalate) (PET) has excellent basic properties, this polymer tends to crystallize rapidly and has a rather high melting temperature, a low glass‐transition temperature, and low impact on notched articles for some potential applications. Copolymerization is a reasonable method for improving the properties of PET. 1,4‐cyclohexane dimethanol (CHDM) is one of the most important comonomers for PET. In this research, PET and PET copolymers containing 5–30% CHDM were prepared from comonomer mixtures by two‐step melt polycondensation. The copolymers were synthesized in a home‐made laboratory setup. The first synthesis step was conducted under pressure, and the second was performed in vacuo at a high temperature (230–290°C). The microstructure of the synthesized copolymers was studied with Fourier transform infrared and nuclear magnetic resonance. The comonomer content in the polymer chain was determined from the nuclear magnetic resonance spectrum. The presence of the comonomer in the copolymer chain was random. Differential scanning calorimetry was used to study the thermal properties of the copolymers to detect changes in the polymer properties. CHDM reduced the heat of fusion and melting and glass‐transition temperatures of the PET copolymers. Process modeling was performed with mass balances of different functional groups and species. Equations of mass balances were integrated numerically. Numerical simulation and experimental results were in very good agreement. By modeling, the effects of the reaction temperature and feed molar ratio on the conversion and formation of diethylene glycol were studied. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Effects of polymer‐grafted natural nanocrystals on the structure and mechanical properties of poly(lactic acid): A case of cellulose whisker‐graft‐polycaprolactone
Authors: Lin Ning , Chen Guangjun , Huang Jin , Dufresne Alain , Chang Peter R.
Published: May 2009

In this work, polysaccharide nanocrystals—rodlike cellulose whiskers (CWs)—were surface‐grafted with polycaprolactone (PCL) via microwave‐assisted ring‐opening polymerization, and filaceous cellulose whisker‐graft‐polycaprolactone (CW‐g‐PCL) nanoparticles were produced. Moreover, the resultant nanoparticles were incorporated into poly(lactic acid) (PLA) as a matrix, and they showed superior function for enhancing the mechanical performance of PLA‐based materials in comparison with platelet‐like nanoparticles of starch nanocrystal‐graft‐PCL. The optimal loading level of CW‐g‐PCL was 8 wt %, and this resulted in simultaneous enhancements of the strength and elongation of approximately 1.9‐ and 10.7‐fold, respectively, over those of the neat PLA material. In this case, the rigid CW nanoparticles contributed to the endurance of higher stress, whereas the grafted PCL chains improved the association between the PLA matrix and the CW‐g‐PCL filler and hence facilitated the transfer of stress to the rigid CW nanoparticles. Furthermore, such a fully biodegradable PLA‐based nanocomposite shows great potential for environmentally friendly materials because of its high mechanical performance. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Self‐reinforcing isotactic polypropylene prepared using crystallizable solvents
Authors: Yoon Joonsung , McCarthy Thomas J. , Lesser Alan J.
Published: May 2009

A new approach to reinforce and toughen isotactic polypropylene (iPP) with improved processability is evaluated. The concept involves using a crystallizable solvent that, at process temperatures melts, is miscible with the polymer thereby reducing its process viscosity. As the polymer cools, the solvent undergoes thermally induced phase separation (TIPS) to produce crystallites that increase the modulus of the solid through reinforcement and promote an increase in impact resistance by mechanisms similar to rubber‐toughened materials. Tetrabromobisphenol‐A (TBBPA) is introduced to iPP that forms a homogeneous mixture at elevated temperature and acts as a processing aid, but undergoes phase separation and subsequent crystallization upon cooling to form rigid particles which, in turn, acts as a toughening agent at room temperature. A phase diagram constructed with Flory‐Huggins solution thermodynamics shows good agreement with the experimental results. The steady state shear viscosity decreases as TBBPA content increases for the mixtures in melt state, indicating improved processability. The decrease in viscosity enhances crystallization rate of iPP significantly, most likely due to increased diffusivity, while the structure of iPP crystals remain unchanged. Tensile tests show that as TBBPA content increases (up to 15 wt %), the yield stress decreases while elongation at break increases. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Laboratory investigation of the properties of asphalt modified with epoxy resin
Authors: Yu Jianying , Cong Peiliang , Wu Shaopeng
Published: May 2009

Epoxy asphalts were prepared by mixing styrene–butadiene–styrene (SBS) modified asphalt with epoxy resin. The curing process and morphology of epoxy asphalts were characterized by infrared spectroscopy and fluorescent microscope, respectively. The effects of epoxy resin contents, ratio of curing agent to epoxy resin and curing temperature on properties of epoxy asphalt were investigated. Results indicated that epoxy resin and epoxy asphalt showed similar curing efficiency. Epoxy asphalts can be cured at 120 or 60°C and its viscosity at 120°C can meet the demands of asphalt mixture mixing and paving. The chemical reaction of epoxy resin in epoxy asphalt is slow and reaction occurs not only with the curing agent but also carboxylic acid in epoxy asphalt. The microstructure of epoxy asphalt transforms from the dispersed structure to networks structure with epoxy resin content increasing and phase transition starts when 30 wt % epoxy resin present in asphalt. The softening point and tensile strength of epoxy asphalt increased with epoxy resin contents increasing. The softening point and tensile strength of epoxy asphalt were markedly improved when epoxy resin content was more than 30 wt %, which is attributed to formation of continuous structure of epoxy resin. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Study on partially oxidized sodium alginate with potassium permanganate as the oxidant
Authors: Lu Lingbin , Zhang Ping , Cao Yang , Lin Qiang , Pang Sujuan , Wang Huaming
Published: May 2009

In this article, partial oxidation of sodium alginate with potassium permanganate (KMnO4) was researched successfully. The effects of KMnO4 on the properties of partially oxidized sodium alginate were discussed. It was found that the degree of oxidation and degradation rate of sodium alginate could be controlled by oxidation conditions, as monitored by the reduction of viscosity and decrease of molecular weight. This work provides a new method to obtain partially oxidized alginate and to improve degradability of alginate for biomedical applications. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Structure and properties of closed‐cell foam prepared from irradiation crosslinked silicone rubber
Authors: Liu Pengbo , Liu Daolong , Zou Huawei , Fan Ping , Xu Wen
Published: May 2009

Silicone rubber foam was prepared through crosslinking with electron beam irradiation and foaming by the decomposing of blowing agent azobisformamide (AC) in hot air. The crosslinking and foaming of silicone rubber was carried out separately, which was different from the conventional method of chemical crosslinking and foaming. After foaming, the silicone rubber foam was irradiated again to stabilize the foam structure and further improve its mechanical properties. The effects of irradiation dose before and after foaming, and the amount of blowing agents on the structure and properties of silicone rubber foam were studied. The experimental results show that with the increase of AC content, the average cell diameter of silicone rubber foam increases a little, the foam density decreases to a minimum value when AC content is 10 phr. With the increase of irradiation dose before foaming from 10 to 17.5 kGy, the cell nucleation density of silicone rubber foam increases, the average cell diameter decreases, and the foam density increases. With the increase of irradiation before foaming, the tensile strength, tensile modulus, and the elongation at break of the silicone rubber foam increase. Through irradiation crosslinking again after foaming, the foam density is decreased and the mechanical properties of silicone foam are further improved. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Modification of ramie fiber with an amine‐containing polymer via atom transfer radical polymerization
Authors: Liu Zhao‐Tie , Sun Chang'an , Liu Zhong‐Wen , Lu Jian
Published: May 2009

The covalent bonding of tertiary amine 2‐(dimethylamino)ethyl methacrylate to ramie fiber via atom transfer radical polymerization was obtained with a brominated initiator and the catalyst CuCl/1,10‐phenanthroline. The results reveal that poly[2‐(dimethylamino)ethyl methacrylate] (PDMAEMA) was successfully immobilized on the surface of the ramie fiber in a controlled polymerization. After the grafting with PDMAEMA, the crystal structure of cellulose I in the ramie fiber was still preserved, and the lateral size of the microfibrils, calculated on the basis of plane 002, was slightly increased. As a demonstration of possible applications, the modified fiber was dyed with CI Reactive Red 2. The dye uptake, which almost linearly increased with increasing molecular weight of PDMAEMA attached on the ramie fiber, was raised to be over 15 times that of the raw fiber. The reason was that the reactivity between the tertiary amines in PDMAEMA and the dichlorotriazinyl group in the dye molecules was much higher than that between the hydroxyl groups in the ramie fiber and the reactive groups in the dye molecules. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Polymers based on N,N‐diglycidylaniline. I. Investigations of the curing kinetics by dynamic differential scanning calorimetry measurements
Authors: Janeczek Henryk , Siwy Mariola , Schab‐Balcerzak Ewa
Published: May 2009

N,N‐Diglycidylaniline was reacted with aniline (yielding polymer EP‐1) and the newly synthesized chromophore 4‐(phenylazo)aniline (yielding polymer EP‐2). The curing kinetics of these two epoxy resin systems was studied in dynamic experiments by means of differential scanning calorimetry. Kinetic parameters such as the activation energy and frequency factor were estimated with the Ozawa method [E(O) and A(O), respectively], the Kissinger method [E(K) and A(K), respectively], and the modified Avrami method [E(A) and A(A), respectively]. The activation energy and frequency factor of EP‐1 were much lower than those of EP‐2 estimated with the Ozawa, Kissinger, and Avrami methods. The activation energy and frequency factor for EP‐1 determined with the Ozawa method [E(O) = 55.8 kJ/mol, A(O) = 10 × 103 1/s] and the Avrami method [E(A) = 56.4 kJ/mol, A(A) = 9.2 × 103 1/s] were higher than those determined with the Kissinger method [E(K) = 51.0 kJ/mol, A(K) = 2 × 103 1/s]. In the case of EP‐2, the kinetic parameters calculated with the Ozawa model [E(O) = 140.4 kJ/mol, A(O) = 12.3 × 1013 1/s] and the Kissinger model [E(K) = 139.9 kJ/mol, A(K) = 10.9 × 1013 1/s] were higher than those calculated with the Avrami model [E(A) = 130.4 kJ/mol, A(A) = 7.9 × 1012 1/s]. The obtained polymers were characterized with Fourier transform infrared, 1H‐NMR, differential scanning calorimetry, and ultraviolet–visible spectroscopy. The polymers exhibited low glass‐transition temperatures in the range of 57–79°C and good solubility in common organic solvents. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Morphology, mechanical properties, and thermal stability of poly(L‐lactic acid)/poly(butylene succinate‐co‐adipate)/silicon dioxide composites
Authors: Wang Ruyin , Wang Shifeng , Zhang Yong
Published: May 2009

Poly(butylene succinate‐co‐adipate) (PBSA) and two types of SiO2 (hydrophilic or hydrophobic) were used to modify poly(L‐lactic acid) (PLLA). The mechanical properties, rheological and thermal behavior, phase morphology, and thermal stability of PLLA/PBSA/SiO2 composites were investigated. The impact strength, flexural strength, and modulus of PLLA/PBSA blends increased after the addition of hydrophobic SiO2 without decreasing the elongation at break, and the elongation at break monotonically decreased with increasing hydrophilic SiO2 content. The melt elasticity and viscosity of the PLLA/PBSA blend increased with the addition of SiO2. The hydrophilic SiO2 was encapsulated by the dispersed PBSA phase in the composites, which led to the formation of a core–shell structure, whereas the hydrophobic SiO2 was more uniformly dispersed and mainly located in the PLLA matrix, which was desirable for the optimum reinforcement of the PLLA/PBSA blend. The thermogravimetric analysis results show that the addition of the two types of SiO2 increased the initial decomposition temperature and activation energy and consequently retarded the thermal degradation of PLLA/PBSA. The retardation of degradation was prominent with the addition of hydrophobic SiO2. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Alkaline‐developable, chemically amplified, negative‐type photosensitive polyimide based on polyhydroxyimide, a crosslinker, and a photoacid generator
Authors: Saito Yuta , Mizoguchi Katsuhisa , Higashihara Tomoya , Ueda Mitsuru
Published: May 2009

A chemically amplified photosensitive polyimide based on polyhydroxyimide (PHI) from cyclobutanetetracarboxylic dianhydride and 4,4′‐(hexafluoroisopropylidene)bis(2‐aminophenol), 4,4′‐methylenebis[2,6‐bis(hydroxymethyl)phenol] (MBHP) as a crosslinker, and (5‐propylsulfonyloxyimino‐5H‐thiophen‐2‐ylidene)‐(2‐methylphenyl)acetonitrile (PTMA) as a photoacid generator was developed to obtain the abilities of low temperature patterning, low dielectric constant, and high sensitivity. The chemically amplified photosensitive polyimide, consisting of PHI (70 wt %), MBHP (20 wt %), and PTMA (10 wt %), showed a high sensitivity (D0.5) of 5.9 mJ/cm2 and a good contrast (γ0.5) of 3.9, respectively, producing a clear negative‐tone line‐and‐space pattern with 6‐μm resolution. Furthermore, the chemically amplified photosensitive polyimide showed a high transparency in the i‐line region and a low dielectric constant of 2.54. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Humic acid/polypyrrole on a paraffin‐impregnated graphite electrode and its use in arsenic extraction
Authors: Antilén M. , Armijo F.
Published: May 2009

A novel and simple electrode with rapid preparation was developed with humic acid (HA) and polypyrrole (PPy) films. The method for modified electrode preparation embraced the abrasive transfer technique on a paraffin‐impregnated graphite electrode (PIGE) followed by the electrochemical incorporation of a PPy polymeric film upon bare PIGE and PIGE/HA electrodes. Cyclic voltammetry, electrochemical impedance spectroscopy, and chronoamperometry were used for the study of the modified electrodes. Morphological characterization was performed by scanning electron microscopy. The obtained results demonstrated that the presence of HA did not affect the electrical properties of the system but indeed provoked changes in the polymer morphology, turning it more granular. Next, PIGE/HA/PPy was tested in arsenic solutions [As(V)] because arsenic contamination of water is an important worldwide environmental issue because of the sources of arsenic contamination of water come from both natural processes and anthropogenic activities. The modified electrode displayed good and reversible extraction properties toward the analyte in acid medium and was 18% more efficient than a previously reported PPy‐modified electrode (PIGE/PPy). From an environmental standpoint, this novel application of conductive polymer properties with the chelating capacity of humic substances constitutes a first step in the development of more efficient technologies for the removal of contaminants present in soil–water media. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009