bluuebunny/crossref_metadata_2025_split huggingface dataset:
Starch esters with improved mechanical properties through melt compounding with nanoclays
Authors: Hassan Nejad Mehdi , Ganster Johannes , Volkert Bert 
Published: May 2010

AbstractBiobased nanocomposites were manufactured through the melt intercalation of nanoclays and starch esters synthesized at the Fraunhofer Institute for Applied Polymer Research (IAP) from high amylose starch. Starch acetates (SAs) and starch propionates (SPs) were tested in combination with glycerol triacetate (triacetin) as a plasticizer for concentrations up to 30 and 20 wt %, respectively, with different types of organomodified and unmodified montmorillonites (MMTs). The mechanical properties of injection‐molded test bars were determined by a tensile experiment giving the strength, modulus, and elongation of the composites. X‐ray diffraction (XRD) analysis and transmission electron microscopy (TEM) were used to study clay dispersion and intercalation/exfoliation. Dynamic mechanical analysis was used to track the temperature dependence of the storage modulus and tan δ behavior of the starch/clay hybrid. Because they were the best performing compositions, SP with 5 wt % plasticizer and SA with 20 wt % plasticizer were filled with 5 wt % nanoclay. For SP, a certain increase in modulus was observed for all clays. However, the strength was practically unchanged, and the elongation decreased in most cases. One exception was found for the 2.5 wt % organomodified clay composition, where the elongation increased. For SA, the addition of 5 wt % nanoclay always increased the strength and modulus, in one case up to 60 and 75%, respectively. In the particular case with 5 wt % unmodified clay, the strength, modulus, and elongation increased by 30, 40, and 1000%, respectively. This was a dramatic improvement in the ductility of the material without losses in the strength and stiffness. XRD and TEM revealed the existence of exfoliated modified clay throughout the starch matrix, whereas for the unmodified case (with the exceptional increase in the elongation), no intercalation was observed. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Solid‐state mechanical properties of polypropylene/nylon 6/clay nanocomposites
Authors: Somwangthanaroj A. , Ubankhlong W. , Tanthapanichakoon W. 
Published: May 2010

AbstractThe mechanical and thermomechanical properties as well as microstructures of polypropylene/nylon 6/clay nanocomposites prepared by varying the loading of PP‐MA compatibilizer and organoclay (OMMT) were investigated. The compatibilizer PP‐MA was used to improve the adhesion between the phases of polymers and the dispersion of OMMT in polymer matrix. Improvement of interfacial adhesion between the PP and PA6 phases occurred after the addition of PP‐MA as confirmed by SEM micrographs. Moreover, as shown by the DSC thermograms and XRD results, the degree of crystallinity of PA6 decreased in the presence of PP‐MA. The presence of OMMT increased the tensile modulus as a function of OMMT loading due to the good dispersion of OMMT in the matrix. The insertion of polymer chains between clay platelets was verified by both XRD and TEM techniques. The viscosity of the nanocomposites decreased as PP‐MA loading increased due to the change in sizes of PA6 dispersed phase, and the viscosity increased as OMMT loading increased due to the interaction between the clay platelets and polymer chains. The clay platelets were located at the interface between PP and PA6 as confirmed by both SEM and TEM. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Thermal decomposition kinetics of azomethine oligomer and its some metal complexes
Authors: Doğan Fatih , Kaya İsmet , Bilici Ali , Saçak Mehmet 
Published: May 2010

AbstractIn our previous study, we presented the synthesis, characterization, and some physical properties of a new azomethine oligomer and its some metal complexes. This study focuses on the thermal decomposition kinetics of these reported materials. The studied compounds were 1,4‐bis[(2‐hydroxyphenyl)methylene]phenylenediamine, oligo‐1,4‐bis[(2‐hydroxyphenyl)methylene] phenylenediamine, and oligo‐1,4‐bis[(2‐hydroxyphenyl)methylene]phenylenediamine–metal complexes. Several kinetic methods based on a single heating rate such as Coats‐Redfern, MacCallum‐Tanner, van Krevelen, Horowitz‐Metzger, Wanjun‐Yuwen‐Hen‐Cunxin, and Madhusudanan‐Krishnan‐Ninan were used to elucidate the kinetic parameters of the decomposition processes. The parameters such as activation energy E, frequency factor A, reaction order n, entropy change ΔS*, enthalpy change ΔH*, and Gibbs free energy change ΔG* were calculated by means of the above methods. The activation energy values obtained by each method were in good agreement with each other. An appropriate mechanism for the thermal decomposition process of each material was also determined by means of the thermogravimetric analysis. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Aliphatic polyamidoamine hyperbranched polymers/layered silicate nanocomposites
Authors: Amin A. , Taha A. S. , Abd El‐Ghaffar M. A. 
Published: May 2010

AbstractPolyamidoamine hyperbranched polymer (Hyp)/clay nanocomposites were synthesized by using both of montmorillonite and laponite clays. Poly amidoamine hyperbranched polymer (Hyp) was prepared by one‐pot polymerization via couple monomer methodology. Afterward, the amino ends of Hyp were modified with methyl methacrylate (MMA), styrene (St) and butyl methacrylate (n‐BuMA) polymers which were previously prepared via ATRP (atom transfer radical polymerization) to form the corresponding new hyperbranched polymers Hyp1, Hyp2 and Hyp3. Those formed polymers were inserted into the modified clay, such as montmorillonite and laponite to form their nanocomposites. The formed polymer/clay nanocomposites were characterized via XRD, TEM, and thermal analyses. The formed hyperbranched polymers generally showed intercalation behavior more than the exfoliation one mostly because of the bulkiness of the hyperbranched skeleton. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Controlling the architecture of nanofiber‐coated microfibers using electrospinning
Authors: Thorvaldsson Anna , Engström Jonas , Gatenholm Paul , Walkenström Pernilla 
Published: May 2010

AbstractThis study shows that electrospinning nanofibers onto single microfibers allows for careful tailoring of material properties that may suit a wide variety of applications. The nanofiber‐coated microfibers are created by electrospinning nanofibers alongside a microfiber toward a collector that rotates around the microfiber. This force the nanofibers to be collected around the microfiber, creating a hierarchical structure that can be modified at nano scale. In this study, control of nanofiber diameters, nanofiber alignment, and nanofiber loading was evaluated. It was seen that varying polymer concentration affected the nanofiber diameters, collecting the nanofiber‐coated microfibers at different speeds changed the degree of alignment of the nanofibers and that changing the polymer feeding rate affected the loading density of the nanofibers collected. The carefully designed nanofiber‐coated microfibers have great potential in creation of highly porous materials with tailored properties down to nano scale. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Simple method to determine flow characteristics of injectable hydrogels
Authors: Nadarajan Sundar Babu , Nguyen An , Kolb James Thomas , Stepanskiy Leonard , Papazoglou Elisabeth S. 
Published: May 2010

AbstractThis article presents a simple inexpensive method to measure flow and viscoelastic properties of calcium alginate hydrogels or gel solutions and is particularly suitable for quality control in small laboratory settings. This method can be considered an extension of the Melt Flow Index (MFI) method, which is routinely used in the polymer industry to indirectly determine the molecular weight of polymers. Results of alginate gels at various crosslinking densities obtained with this new test are compared to complex viscosity data obtained from a standard cone and plate rheometer, and demonstrate very good correlation. A mathematical model describing the apparent viscosity of the alginate gels in this test has also been developed. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Retracted: Isolation and chemical structure characterization of enzymatic lignin from Populus deltoides wood
Authors: Abdulkhani Ali , Karimi Alinaghi , Mirshokraie Ahmad , Hamzeh Yahya , Marlin Nathalie , Mortha Gerard 
Published: May 2010

AbstractThe following article from the Journal of Applied Polymer Science, “Isolation and chemical structure characterization of enzymatic lignin from Populus deltoides wood,” by Ali Abdulkhani, Alinaghi Karimi, Ahmad Mirshokraie, Yahya Hamzeh, Nathalie Marlin, and Gerard Mortha, published online on 21 May 2010 in Wiley Online Library (wileyonlinelibrary.com), and in Volume 118, pp. 469‐479, has been retracted by agreement between the authors, the journal's editors, and Wiley Periodicals, Inc. The retraction has been agreed due to unacknowledged overlap between Figure 5 in the above paper and Figure 1 in Industrial Crops and Products, Volume 30 (2009), p. 137, as well as inappropriate data manipulation associated with this figure. The publisher acknowledges that co‐authors Nathalie Marlin and Gerard Mortha are not responsible for the issues associated with this article.
Effect of organoclay reinforcement on the curing characteristics and technological properties of SBR sulphur vulcanizates
Authors: Diez J. , Bellas R. , Ramírez C. , Rodríguez A. 
Published: May 2010

AbstractStyrene‐butadiene rubber (SBR) nanocomposites with different organoclay contents (up to 15 phr) were prepared by a melt compounding procedure, followed by a compression‐molding step in which the SBR matrix was sulfur crosslinked. The vulcanizates were characterized in respect to their curing, mechanical and viscoelastic properties, and thermal stability. The optimum cure time decreased with increasing organoclay content. This effect was attributed to the ammonium modifier present in the organoclay, which takes part in the curing reaction acting like an accelerator. The results of mechanical test on the vulcanizates showed that the nanocomposites presented better mechanical properties than unfilled SBR vulcanizate, indicating the nanoreinforcement effect of clay on the mechanical properties of SBR/organoclay nanocomposites. The addition of organoclay did not significantly change the glass transition temperature. However, the heights of tan δ value at the glass transition temperature for the nanocomposites are lower than that of the unfilled SBR. This suggests a strong interaction between the organoclay and the SBR matrix as the molecular relaxation of the latter is hampered. The temperature at which 50% degradation occurs (T50) and the temperature when the degradation rate is maximum (DTGmax) showed an improvement in thermal stability, probably related to the uniform dispersion of organoclay. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Impact behavior of hybrid composite plates
Authors: Sayer Metin , Bektaş Numan Behlül , Çallioğlu Hasan 
Published: May 2010

AbstractThis experimental study deals with the impact response of hybrid composite laminates. Two different hybrid composite laminates, aramid/glass and aramid/carbon, and two different stacking sequences, such as [0/0/90/90]A+ [90/90/0/0]G for AG1 and [0/90/±45]A+ [±45/90/0]G for AG2 and so on (see Table I), were chosen for impact testing. The impact energy was gradually increased until complete perforation took place, and an energy profiling method (EPM) was used to identify the perforation thresholds of composites. The damaged samples were visually inspected. The images of the several samples subjected to various impact energies were registered and used for comparison and identifying damage mechanisms. The perforation thresholds for [0/90/±45]s aramid/glass and aramid/carbon laminates were found to be approximately 5% higher than those for their counterparts with the [0/0/90/90]s stacking sequence. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Hypoxia‐inducible factor regulation of ANK expression in nucleus pulposus cells: Possible implications in controlling dystrophic mineralization in the intervertebral disc
Authors: Skubutyte Renata , Markova Dessislava , Freeman Theresa A. , Anderson D. Greg , Dion Arnold S. , Williams Charlene J. , Shapiro Irving M. , Risbud Makarand V. 
Published: May 2010

AbstractObjectiveSince nucleus pulposus cells reside under conditions of hypoxia, we determined if the expression of ANK, a pyrophosphate transporter, is regulated by the hypoxia‐inducible factor (HIF) proteins.MethodsQuantitative reverse transcription–polymerase chain reaction and Western blot analyses were used to measure ANK expression in nucleus pulposus cells from rats and humans. Transfections were performed to determine the effect of HIF‐1/2 on ANK promoter activity.ResultsANK was expressed in embryonic and mature rat discs. Oxygen‐dependent changes in ANK expression in nucleus pulposus cells were minimal. However, silencing of HIF‐1α and HIF‐2α resulted in increased ANK expression and up‐regulation of promoter activity. HIF‐mediated suppression of ANK was validated by measuring promoter activity in HIF‐1β–null embryonic fibroblasts. Under conditions of hypoxia, there was induction of promoter activity in the null cells as compared with the wild‐type cells. Overexpression of HIF‐1α and HIF‐2α in nucleus pulposus cells resulted in a significant suppression of ANK promoter activity. Since the ANK promoter contains 2 hypoxia‐responsive elements (HREs), we performed site‐directed mutagenesis and measured promoter activity. We found that HIF‐1 can bind to either of the HREs and can suppress promoter activity; in contrast, HIF‐2 was required to bind to both HREs in order to suppress activity. Finally, analysis of human nucleus pulposus tissue showed that while ANK was expressed in normal tissue, there was increased expression of ANK along with alkaline phosphatase in the degenerated state.ConclusionBoth HIF‐1 and HIF‐2 serve as negative regulators of ANK expression in the disc. We propose that baseline expression of ANK in the disc serves to prevent mineral formation under physiologic conditions.
Phase‐Controlled Synthesis of Transition‐Metal Phosphide Nanowires by Ullmann‐Type Reactions
Authors: Wang Junli , Yang Qing , Zhang Zude , Sun Shouheng 
Published: May 2010

AbstractTransition‐metal phosphide nanowires were facilely synthesized by Ullmann‐type reactions between transition metals and triphenylphosphine in vacuum‐sealed tubes at 350–400 °C. The phase (stoichiometry) of the phosphide products is controllable by tuning the metal/PPh3 molar ratio and concentration, reaction temperature and time, and heating rate. Six classes of iron, cobalt, and nickel phosphide (Fe2P, FeP, Co2P, CoP, Ni2P, and NiP2) nanostructures were prepared to demonstrate the general applicability of this new method. The resulting phosphide nanostructures exhibit interesting phase‐ and composition‐dependent magnetic properties, and magnetic measurements suggested that the Co2P nanowires with anti‐PbCl2 structure show a ferromagnetic–paramagnetic transition at 6 K, while the MnP‐structured CoP nanowires are paramagnetic with Curie–Weiss behavior. Moreover, GC‐MS analyses of organic byproducts of the reaction revealed that thermally generated phenyl radicals promoted the formation of transition‐metal phosphides under synthetic conditions. Our work offers a general method for preparing one‐dimensional nanoscale transition‐metal phosphides that are promising for magnetic and electronic applications.
How Post‐Translational Modifications Influence Amyloid Formation: A Systematic Study of Phosphorylation and Glycosylation in Model Peptides
Authors: Broncel Malgorzata , Falenski Jessica A. , Wagner Sara C. , Hackenberger Christian P. R. , Koksch Beate 
Published: May 2010

AbstractA reciprocal relationship between phosphorylation and O‐glycosylation has been reported for many cellular processes and human diseases. The accumulated evidence points to the significant role these post‐translational modifications play in aggregation and fibril formation. Simplified peptide model systems provide a means for investigating the molecular changes associated with protein aggregation. In this study, by using an amyloid‐forming model peptide, we show that phosphorylation and glycosylation can affect folding and aggregation kinetics differently. Incorporation of phosphoserines, regardless of their quantity and position, turned out to be most efficient in preventing amyloid formation, whereas O‐glycosylation has a more subtle effect. The introduction of a single β‐galactose does not change the folding behavior of the model peptide, but does alter the aggregation kinetics in a site‐specific manner. The presence of multiple galactose residues has an effect similar to that of phosphorylation.
Electrophilicity versus Electrofugality of Tritylium Ions in Aqueous Acetonitrile
Authors: Horn Markus , Mayr Herbert 
Published: May 2010

AbstractFirst‐order rate constants kw for the reactions of a series of donor‐substituted triphenylmethylium (tritylium) ions with water in aqueous acetonitrile have been determined photometrically at 20 °C using stopped‐flow and laser‐flash techniques. The rate constants follow the linear free energy relationship log k(20 °C)=s(N+E). The reactivities kw of the methyl‐ and methoxy‐substituted tritylium ions towards water correlate linearly with the corresponding pK values with a Leffler–Hammond coefficient α=δΔG≠/δΔG0 of 0.62. The amino‐substituted compounds react more slowly than expected from the correlation of the less stabilized systems. Quantum chemical calculations of tritylium ions and the corresponding triarylmethanols and 1,1,1‐triarylethanes have been performed at the MP2(FC)/6‐31+G(2d,p)//B3LYP/6‐31G(d,p) level. The calculated gas‐phase hydroxide and methyl anion affinities of the tritylium ions correlate linearly with a slope of unity, indicating that the relative anion affinities do not depend on the nature of the anion. The pK values of the methyl‐ and methoxy‐substituted tritylium ions correlate linearly with the calculated gas‐phase hydroxide affinities, and the slope of this correlation shows that the differences in carbocation stabilities in the gas phase are attenuated to 66 % in solution. Mono‐ and bis(dimethylamino)‐substituted derivatives deviate from this correlation; their pK values are higher than expected from their calculated gas‐phase hydroxide affinities, which is explained by the extraordinary solvation of unsymmetrically amino‐substituted tritylium ions. Complete free‐energy profiles for the solvolyses of substituted trityl benzoates in 90:10 (v/v) acetonitrile/water have been constructed.
Fabrication of Large‐Scale Hierarchical ZnO Hollow Spheroids for Hydrophobicity and Photocatalysis
Authors: Sinha Arun Kumar , Basu Mrinmoyee , Pradhan Mukul , Sarkar Sougata , Pal Tarasankar 
Published: May 2010

AbstractWe report here the preparation of a crystalline, pure hexagonal phase of ZnO as hollow 500–800 nm spheroids in the presence of organic bases, such as pyridine, using zinc acetate as the precursor salt. The spheroids exhibit unique 3D hierarchical architectures, like cocoons, and demonstrate improved superhydrophobic (water contact angle, 150°) character due to the inherited air‐trapped capillarity within the cocoon structure. The simple synthetic strategy used in this process is modified hydrothermolysis (MHT), which represents a general approach and may contribute to the formation mechanism of the hollow nanostructures with highly improved porosity. Depending on the concentration of the precursor salt, it has been possible to cover glass plates or the inner wall of a reaction vessel with ZnO nanocrystals. A low salt concentration (<0.01 M) allows the easy preparation of a superhydrophobic glass surface, whereas a high salt concentration (>0.01 M) results in the precipitation of cocoons at the bottom of the reaction vessel as a solid mass together with a deposited thin film of ZnO nanocrystals covering the inner wall of the glass vessel. The thickness of the film successively grows through repetitive hydrothermolysis processes for which a low salt concentration (<0.01 M) was employed. Because of the hollow cocoonlike morphology, the surface area of the film is greatly increased, which makes it accessible for functionalization by incoming substrates from both sides (internally and externally) and helps to drive a competent photocatalytic dye degradation pathway. The heterocyclic base pyridine exclusively develops cocoons. Thus, the mechanism of self‐aggregation of ZnO nanocrystals under MHT reaction conditions has been studied and the characterization of the compounds has been supported with physical measurements.
Ligand–Receptor Binding Affinities from Saturation Transfer Difference (STD) NMR Spectroscopy: The Binding Isotherm of STD Initial Growth Rates
Authors: Angulo Jesús , Enríquez‐Navas Pedro M. , Nieto Pedro M. 
Published: May 2010

AbstractThe direct evaluation of dissociation constants (KD) from the variation of saturation transfer difference (STD) NMR spectroscopy values with the receptor–ligand ratio is not feasible due to the complex dependence of STD intensities on the spectral properties of the observed signals. Indirect evaluation, by competition experiments, allows the determination of KD, as long as a ligand of known affinity is available for the protein under study. Herein, we present a novel protocol based on STD NMR spectroscopy for the direct measurements of receptor–ligand dissociation constants (KD) from single‐ligand titration experiments. The influence of several experimental factors on STD values has been studied in detail, confirming the marked impact on standard determinations of protein–ligand affinities by STD NMR spectroscopy. These factors, namely, STD saturation time, ligand residence time in the complex, and the intensity of the signal, affect the accumulation of saturation in the free ligand by processes closely related to fast protein–ligand rebinding and longitudinal relaxation of the ligand signals. The proposed method avoids the dependence of the magnitudes of ligand STD signals at a given saturation time on spurious factors by constructing the binding isotherms using the initial growth rates of the STD amplification factors, in a similar way to the use of NOE growing rates to estimate cross relaxation rates for distance evaluations. Herein, it is demonstrated that the effects of these factors are cancelled out by analyzing the protein–ligand association curve using STD values at the limit of zero saturation time, when virtually no ligand rebinding or relaxation takes place. The approach is validated for two well‐studied protein–ligand systems: the binding of the saccharides GlcNAc and GlcNAcβ1,4GlcNAc (chitobiose) to the wheat germ agglutinin (WGA) lectin, and the interaction of the amino acid L‐tryptophan to bovine serum albumin (BSA). In all cases, the experimental KD measured under different experimental conditions converged to the thermodynamic values. The proposed protocol allows accurate determinations of protein–ligand dissociation constants, extending the applicability of the STD NMR spectroscopy for affinity measurements, which is of particular relevance for those proteins for which a ligand of known affinity is not available.