bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electrodeposition of zinc on AZ91D magnesium alloy pre‐treated by stannate conversion coatings
Authors: Zhang S. Y. , Li Q. , Chen B. , Xu S. Q. , Fan J. M. , Luo F. 
Published: December 2009

AbstractA stannate chemical conversion process followed by an activation procedure was employed as the pre‐treatment process for AZ91D magnesium alloy substrate. Zn was electroplated onto the pre‐treated AZ91D magnesium alloy surface from pyrophosphate bath to improve the corrosion resistance and the solderability. The surface morphologies of conversion coating and zinc coating were examined with scanning electron microscope (SEM). The phase composition of conversion coating was investigated by X‐ray diffraction (XRD). The electrochemical corrosion behavior of the coatings in the corrosive solution was investigated by potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS). The experimental results showed that the activated stannate chemical conversion coating provided a suitable interface between zinc coating and the AZ91D magnesium alloy substrate. The corrosion resistance of the AZ91D substrate was improved by the zinc coating.
A mathematical model for prediction of time from corrosion initiation to corrosion cracking in RC structures
Authors: Lin G. , Liu Y. H. , Xiang Z. H. 
Published: December 2009

AbstractPrediction of time from corrosion initiation to corrosion cracking is a crucial factor in evaluating concrete structures' durability and integrity deteriorated by reinforcement corrosion. This paper presents a mathematical model to predict the time from corrosion initiation to corrosion cracking. A dynamic corrosion rate model based on Bulter–Volmer kinetics and a rust expansion model based on Faraday's law are developed. An analytical model is developed to demonstrate the mechanical consequences of rust buildup around the rebar. The time to corrosion cracking is found to be a function of surrounding concrete material properties, chemical composition of rust, ratio of concrete cover thickness to rebar diameter, and corrosion current density. Comparisons with available experimental results are conducted to show the accuracy and reliability of the present model. Further parametric analysis is carried out to show the influences of various parameters included in the model on the time to corrosion cracking.
Morphology of Novel PEAs Containing Two Consecutive Amide Bonds Randomly Distributed Along the Polyester Backbone
Authors: Garg Priya , Lohakare Pratiksha , Mela Petra , Möller Martin , Blümich Bernhard , Adams Alina 
Published: December 2009

AbstractThe morphology of a series of novel segmented PEAs with varying amide content was studied by a combination of DSC, SFM and proton solid state NMR. Semicrystalline polymers organised in a lamellar morphology were obtained for all amide contents. The results of different NMR experiments revealed that a three phase system composed of a rigid phase, an interface and a mobile amorphous phase is the most appropriate model to describe the morphology of these materials. The amount, the chain dynamics and the domain size of each phase were estimated and correlated with the amount of the amide fraction. Such morphological investigations help to understand the macroscopic properties of segmented PEAs for their applications as biomaterials.magnified image
Benzoylgermanium Derivatives as Novel Visible‐Light Photoinitiators for Dental Composites
Authors: Moszner Norbert , Zeuner Frank , Lamparth Iris , Fischer Urs Karl 
Published: December 2009

AbstractNew dibenzoylgermanium derivatives are synthesized starting from various dithioacetal protected benzaldehydes by a coupling reaction with different dialkyldichlorogermanes and subsequent oxidative cleavage of the protecting group. The synthesized germanium compounds show a significantly stronger blue light absorption than camphorquinone. During irradiation, the dibenzoylgermanium derivatives undergo photodecomposition under formation of radicals. Therefore, the different dibenzoylgermanium derivatives are used as amine‐free visible‐light photoinitiators for dental cements and composites. Composites based on the different dibenzoylgermanes are storage‐stable and show a significantly improved bleaching behavior over composites with CQ/amine photoinitiators.magnified image
Computer Simulations of Natural and Synthetic Polymers in Confined Systems
Authors: Piotto S. , Concilio S. , Mavelli F. , Iannelli P. 
Published: December 2009

AbstractNanotechnology is the ability to work at the molecular and supramolecular levels in order to create and use devices, structures and systems with the desired properties and functions. This is what Nature already does in living systems. In this work we investigated the consequences of confinement in the ordering of natural (namely proteins) and synthetic polymers by means of computational techniques. The focus is put on the possibility to design new materials in a Nature‐like fashion. In the first part of the paper, the possibility to select/design different folding of the same peptide is investigated by means of full atoms molecular dynamics. In the second part of the paper dynamic mean‐field density functional method is applied to the dynamics of block copolymer melts in three‐dimensional lattice model. The analysis of the aggregates and their temporal evolution in free space and in confined space are compared.
Synthesis and Characterization of Composite Materials HDPE/HA and PMMA/HA Prepared by Sonochemistry
Authors: Parra C. , González G. , Albano C. 
Published: December 2009

AbstractSummary: In the present work, the synthesis and characterization of composite materials based on HDPE, and PMMA with nanometric hydroxyapatite, are studied. Composites preparation was carried out by dilutions of the commercial polymers, using decaline as solvent for the polyolefin and 2‐butanone for PMMA. In the synthesis of Hydroxyapatite (HA), ammonium phosphate [(NH4)2HPO4] and calcium hydroxide [Ca(OH)2] were used as precursors. Composites with 20, 30 and 40 wt% of HA were prepared. The polymer dilutions and the precursors of the HA were placed simultaneously in a reactor under ultrasonic radiation at 20 kHz, for periods of 15, 25 and 35 min. The products obtained were characterized by FTIR, TGA, TEM, XRD and biocompatibility studies were also carried out. The results showed the presence of nanometric HA and clear interactions between HA and PMMA polymers were observed by FTIR. These results were corroborated by TEM showing that nanometric HA particles are encapsulated into the polymeric PMMA matrix. For the composites of HDPE, these interactions were not observed.
HDPE‐Coconut Flour Composites: Effect of Coupling Agents and Surface Modification
Authors: Albano C. , González J. , Hernández M. , Ichazo M. N. , Alvarado S. , Ziegler D. M. , Lavadi M. 
Published: December 2009

AbstractThis research work studies the mechanical, thermal and morphological behavior of coconut flour/polyethylene composites, with special emphasis on the influence of the surface modification of coconut flour and the presence of different coupling agents on the interfacial bonding. The different treatments of the composites with an EAA copolymer, with 5 and 18 wt% of NaOH and acetylation, confirm the better tensile behavior of these composites.
Synthesis and Characterization of Polymeric Materials from Vegetable Oils
Authors: Lopes Roseany V. V. , Loureiro Nuno Pedro D. , Zamian José R. , Fonseca Pâmela S. , Macedo Júlio L. , dos Santos Maria L. , Sales Maria J. A. 
Published: December 2009

AbstractAlthough the petrochemical polymers have revolutionized the technological development, the intensive use of these materials have contributed to the global pollution. In this context, researches involving ecofriendliness materials are growing up, as well as, a current interest in developing materials from inexpensive and renewable resources, such as vegetable oils. In this work, is described the synthesis of polymeric materials by thermal polymerization from linseed oil (Linum usitatissimum L.) and passion fruit oil (Passiflora edulis) and their characterization by gas chromatographic (GC), Fourier transform infrared (FTIR) spectroscopy, solubility in organic solvents, thermogravimetry (TG), differential scanning calorimetry (DSC) and Raman spectroscopy. The TG curve shows that those polymeric materials present two stages of decomposition. DSC plots of the vegetable oils showed some endothermic and exothermic transitions which are not present in the DSC curves corresponding to oil‐based polymers. The Raman spectra of the polymers indicate declining of absorbance in the region of CC stretching (∼1600 cm−1). This absorption was used to estimate the degree of polymerization (79% and 67.5% for linseed and passion fruit oils, respectively).
Mechanical Properties and Dynamic Mechanical Analysis of Thermoplastic‐Natural Fiber/Glass Reinforced Composites
Authors: Di Landro Luca , Lorenzi William 
Published: December 2009

AbstractThe mechanical properties and dynamic behavior of thermoplastic composites based on polypropylene/glass fibers and polypropylene/natural fibers (i.e. kenaf, hemp, flax) are presented. A survey is given on some aspects, crucial for the use of these composites in structural and non‐structural components such as their vibration‐damping response, in relation to the composite compaction level and the manufacturing procedure. In order to investigate a wide vibration frequency range, including acoustic frequencies, different testing techniques, both with forced and free vibrations, were applied. A comparison between natural fiber and glass fiber reinforced laminates is presented. Compaction levels, allowing to obtain the best compromise between mechanical performance and damping response, are investigated.
In‐Situ Formation of Silver Nanoparticles in PEI
Authors: Cotts S. , Compton J. , Kranbuehl D. , Espuche E. , David L. , Boiteux G. 
Published: December 2009

AbstractNanocomposites consisting of spherical particles of Ag were prepared using a single step in situ method whereby Ag is introduced into the dissolved polymer via dissolution as the organometallic complex Ag TFA in the same solvent as the polymer. The kinetic rate of formation of the particles is determined using WAXS and SAXS measurements. Nanoparticle formation is found to depend on reducing the solvent/polymer ratio, which leads to de‐solvating the metal complex. This destabilizes the metal precursor complex, causing it to degrade and the metal particles to phase separate by a thermodynamic driving force. The size of the nanoparticles varies with the cure temperature and the conditions affecting molecular mobility.
Using Plasma‐Activated High Performance Fibers with Nanocrystalline Structure in Producing New Reinforced Composite Materials
Authors: Kudinov Vladimir V. , Korneeva Natalia V. 
Published: December 2009

AbstractA multifilament wet‐pull‐out method for estimation of physicochemical interaction between the fiber and the matrix in composite materials reinforced with high‐strength high‐modulus polyethylene fiber has been proposed. Controlled parameters are fiber capillary rise h and pull‐out force F. The method allows one to estimate the wettability and multifilament fiber impregnation with the liquid matrix and measure fiber capillary rise and the joint strength after curing process finished. The multifilament wet‐pull‐out method considers a total interaction between the matrix and filaments in a complex fiber or yarn. It is the advantage of this method in comparison with the tests of individual monofilament. The method makes it possible to model the real operating conditions of CM.
Polyethylene and Poly(propylene)/Clay Nanocomposites
Authors: Kubisova Hana , Merinska Dagmar , Svoboda Petr 
Published: December 2009

AbstractPolyethylene and polypropylene nanocomposites were investigated with focus on mechanical and barrier properties. Structure was observed by X‐ray diffraction (XRD) and transmission electron microscopy (TEM). Four types of nano‐filler were used: Nanofil 5, 8, 9 and 3000. In case of polyethylene nanocomposites the dispersion and intercalation was to low extent. Mechanical and barrier properties were worse compared to pure PE. In case of polypropylene with Nanofil 5, 9 and 3000 tensile strength was better compared to pure PP. Also PP with Nanofil 9 and 3000 had better barrier properties than pure PP for both O2 and CO2. This was explained by better intercalation and dispersion of the filler documented by XRD measurement and TEM observation.
Methionine restriction up‐regulates the expression of the pi class of glutathione S‐transferase partially via the extracellular signal‐regulated kinase‐activator protein‐1 signaling pathway initiated by glutathione depletion
Authors: Tsai Chia‐Wen , Lin Ai‐Hsuan , Wang Tsung‐Shing , Liu Kai‐Li , Chen Haw‐Wen , Lii Chong‐Kuei 
Published: December 2009

AbstractUnderstanding the molecular events underlying gene regulation by amino acids has attracted increasing attention. Here, we explored whether the mechanism by which methionine restriction affects the expression of the π class of glutathione S‐transferase (GSTP) is related to oxidative stress initiated by glutathione (GSH) depletion. Rat primary hepatocytes were cultured in an L‐15‐based medium in the absence or presence of 200 μM L‐buthionine sulfoximine (BSO) or in a methionine‐restricted L‐15 medium supplemented with 20 μM L‐methionine up to 72 h. BSO and methionine restriction time‐dependently induced GSTP mRNA and protein expression in a similar pattern accompanied by a decrease in the cellular GSH level. The phosphorylation of extracellular signal‐regulated kinase (ERK), but not of c‐Jun NH2‐terminal kinase and p38, was stimulated by methionine restriction and BSO. Electromobility gel shift assay showed that the DNA‐binding activity of nuclear activator protein‐1 (AP‐1) increased in cells exposed to methionine restriction or BSO. With the ERK inhibitor FR180204, AP‐1 activation and GSTP expression were abolished. Moreover, the induction of GSTP by methionine restriction and BSO was reversed by GSH monoethyl ester and N‐acetylcysteine. Our results suggest that methionine restriction up‐regulates GSTP gene expression, which appears to be initiated by the ERK‐AP‐1 signaling pathway through GSH depletion in rat hepatocytes.
Resveratrol bioavailability and toxicity in humans
Authors: Cottart Charles‐Henry , Nivet‐Antoine Valérie , Laguillier‐Morizot Christelle , Beaudeux Jean‐Louis 
Published: December 2009

AbstractNumerous data are now available on the beneficial properties of the polyphenolic compound resveratrol including its anti‐inflammatory and antitumor effects. However, few studies have been performed with resveratrol in humans, and the results of these studies appear fragmentary and sometimes contradictory due to variations in conditions of administration, protocols and methods of assessment. This review article presents the results of recent studies investigating the pharmacokinetics, bioavailability, and toxicity of resveratrol in humans. Resveratrol is well absorbed, rapidly metabolized, mainly into sulfo and glucuronides conjugates which are eliminated in urine. Resveratrol seems to be well tolerated and no marked toxicity was reported. These data are important in the context of human efficacy studies, and they provide further support for the use of resveratrol as a pharmacological drug in human medicine.
Effect of dietary fat on endocannabinoids and related mediators: Consequences on energy homeostasis, inflammation and mood
Authors: Banni Sebastiano , Di Marzo Vincenzo 
Published: December 2009

AbstractAmong the several known fatty acid‐derived chemical signals, the endogenous ligands of cannabinoid receptors type‐1 and ‐2, two G‐protein‐coupled receptors involved in several aspects of mammalian physiology and pathology, are perhaps those the levels of which have proven to be most sensitive to the fatty acid composition of the diet. The two most studied such ligands, known as endocannabinoids, are N‐arachidonoyl‐ethanolamine and 2‐archidonoylglycerol, and are found in tissues together with other N‐acyl‐ethanolamines and 2‐acylglycerols, not all of which activate the cannabinoid receptors, although several of them do exhibit important pharmacological effects. In this review article, we describe literature data indicating that the tissue concentrations of the endocannabinoids and related signalling molecules, and hence the activity of the respective receptors, can be modulated by modifying the fatty acid composition of the diet, and particularly its content in long chain PUFAs or in long chain PUFA precursors. We also discuss the potential impact of these diet‐induced changes of endocannabinoid tone on three of the major pathological conditions in which cannabinoid receptors have been involved, that is metabolic dysfunctions, inflammation and affective disorders.
Bioraffinerie: Wo kommen die Chemikalien her?
Authors: Kamm Birgit , Gerhardt Mirko , Leiß Sebastian 
Published: December 2009

AbstractMomentan beruht die chemische Wertschöpfungskette auf Erdöl. Um es zu ersetzen, muss ein neuer Produktlinienstammbaum aus nachwachsenden Rohstoffen, insbesondere von Kohlenhydraten, aufgebaut werden. Wichtige Plattformchemikalien dieser neuen Wertschöpfungskette sind Milchsäure und Hydroxymethylfurfural.
”Den glücklichen Zufall einladen“
Authors: Remenyi Christian 
Published: December 2009

AbstractRyoji Noyori erhielt den Chemie‐Nobelpreis 2001 für seine Arbeiten zu asymmetrischen Hydrierungsreaktionen. Der Präsident der japanischen Forschungsorganisation Riken und Chemiker aus Leidenschaft sprach mit den Nachrichten aus der Chemie über Wissenschaft in Japan und die Zukunft der Katalyse.
Chemie für alle
Authors: Gründel Franziska 
Published: December 2009

AbstractWelches Risiko steckt in Nanopartikeln? Wann leuchtet grünfluoreszierendes Protein? Und wie können pflanzliche Rohstoffe Erdöl ersetzen? Damit Studenten und Naturwissenschaftler lernen, Laien solche Fragen zu beantworten und sie für Wissenschaft zu begeistern, bildet die Universität Göttingen seit diesem Semester Chemiestudenten zu Wissenschaftsjournalisten aus.
Der andere Ostwald
Authors: Offermanns Heribert 
Published: December 2009

AbstractDie Leistungen Walter Ostwalds stehen im Schatten seines Vaters Wilhelm. 1909, im selben Jahr in dem der Vater den Nobelpreis erhielt, startete der Automobilfreund Walter Ostwald Untersuchungen zum Autoabgaskatalysator. Doch erst seit 20 Jahren ist die Autoabgasreinigung in Deutschland obligatorisch.
Algebraic multigrid within defect correction for the linearized Euler equations
Authors: Naumovich Anna , Förster Malte , Dwight Richard 
Published: December 2009

AbstractGiven the continued difficulty of developing geometric multigrid methods that provide robust convergence for unstructured discretizations of compressible flow problems in aerodynamics, we turn to algebraic multigrid (AMG) as an alternative with the potential to automatically deal with arbitrary sources of stiffness on unstructured grids. We show here that AMG methods are able to solve linear problems associated with first‐order discretizations of the compressible Euler equations extremely rapidly. In order to solve the linear problems resulting from second‐order discretizations that are of practical interest, we employ AMG applied to the first‐order system within a defect correction iteration. It is demonstrated on two‐ and three‐dimensional test cases in a range of flow regimes (sub‐, trans‐ and supersonic) that the described method converges rapidly and robustly. Copyright © 2009 John Wiley & Sons, Ltd.
Rheology of LDPE‐based semiflexible fiber suspensions
Authors: Keshtkar M. , Heuzey M.‐C. , Carreau P.J. 
Published: December 2009

AbstractMolten LDPE suspensions containing fibers of different flexibilities have been investigated in simple shear and small and large amplitude oscillatory shear (LAOS) flow. The suspensions exhibited viscosity and normal stress overshoots in stress growth experiments, and the magnitude and width of the overshoots became larger as the fiber flexibility increased. LAOS was used to help understanding the relationship between stress growth and fiber orientation. For all composites, the stress signal decreased with time in LAOS, and this behavior was more pronounced in the case of the more rigid fibers. The energy dissipated per LAOS cycle was evaluated for each composite, and it showed that less energy was dissipated as fiber flexibility decreased. In addition, the dissipated energy decreased with time and this has been interpreted in terms of a reduction of fiber contacts. The first normal stress difference showed a nonsinusoidal periodic response, and fast Fourier transform analysis indicated the presence of a first harmonic corresponding to the applied frequency for the fiber‐filled systems, in addition to the second harmonic observed for the neat LDPE. It resulted in asymmetrical strain‐normal force Lissajou curves for the suspensions, with this asymmetry being more pronounced in the case of the more rigid fibers. This has been attributed to a more extensive fiber orientation for the latter. POLYM. COMPOS., 31:1474–1486, 2010. © 2009 Society of Plastics Engineers
Quantitative 3D measurement of the nanostructural features that dictate mesoscale performance properties of nanocomposites
Authors: Mahboob M. , Kagarise C. , Koelling K.W. , Bechtel S.E. 
Published: December 2009

AbstractMesoscale performance properties of nanocomposites are dictated by the nanoscale structure developed in the composite during processing, combining nanoscale contributions over a mesoscale volume. In this artilce, for the first time, we present a procedure that deduces the fully 3D process‐induced nanostructural features of carbon nanofiber/polymer composites responsible for the mesoscale performance. In particular, we have developed a method for obtaining the nanofiber orientation in 3D Euclidean space from 2D projections provided by a transmission electron microscope. The 3D Euler angles we obtain are used to construct orientation tensors, the measure of nanostructure that has the most significant influence on mesoscale performance properties. Our measurement method is benchmarked by using numerically generated 3D samples to compare orientation tensor components known a priori with those generated using our procedure. A significant contribution of the procedure is its ability to produce quantitative 3D measurements of the evolution of nanostructure in space and time. The method is successfully applied to observe the effect of extensional rheology on nanofiber orientation. It is shown that orientation tensor data obtained from our experimental method accurately fits the predictions of the fiber orientation evolution equation proposed by Folgar and Tucker. POLYM. COMPOS., 31:1495–1503, 2010. © 2009 Society of Plastics Engineers
Cure shrinkage characterization of an epoxy resin system by two in situ measurement methods
Authors: Khoun Loleï , Hubert Pascal 
Published: December 2009

AbstractDimensional accuracy of composites manufacturing is a major issue for part producers, especially when tight tolerances are required. One of the main causes of dimensional variations is the resin volumetric changes during the cure. In this article, volumetric cure shrinkage of a one part epoxy system was characterized using two different methods. First, a modified rheology method was used to measure the volumetric cure shrinkage after the gel point. Second, a gravimetric method measured the shrinkage over the entire cure. A linear relationship between the volumetric cure shrinkage and the degree‐of‐cure was deduced from the results and the resin cure kinetic models. Results show a good agreement between the two techniques. POLYM. COMPOS., 31:1603–1610, 2010. © 2009 Society of Plastics Engineers