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Selected AbstractsA preliminary characterization of the mutagenicity of atmospheric particulate matter collected during sugar cane harvesting using the Salmonella/microsome microsuspension assayENVIRONMENTAL AND MOLECULAR MUTAGENESIS, Issue 4 2008Gisela de Aragão Umbuzeiro Abstract During sugar cane harvesting season, which occurs from May to November of each year, the crops are burnt, cut, and transported to the mills. There are reports showing that mutagenic activity and PAH content increase during harvesting season in some areas of São Paulo State in comparison with nonharvesting periods. The objective of this work was to preliminarily characterize the mutagenic activity of the total organic extracts as well as corresponding organic fractions of airborne particulate matter (PM) collected twice from two cities, Araraquara (ARQ) and Piracicaba (PRB), during sugar cane harvesting season using the Salmonella/microsome microssuspension assay. One sample collected in São Paulo metropolitan area was also included. The mutagenicity of the total extracts ranged from 55 to 320 revertants per cubic meter without the addition of S9 and from not detected to 57 revertants per cubic meter in the presence of S9 in areas with sugar cane plantations. Of the three fractions analyzed, the most polar ones (nitro and oxy) were the most potent. A comparison of the response of TA98 with YG1041 and the increased potencies without S9 indicated that nitro compounds are causing the observed effect. More studies are necessary to verify the sources of the mutagenic activity such as burning of vegetal biomass and combustion of heavy duty vehicles used to transport the sugar cane to the mills. The Salmonella/microsome assay can be an important tool to monitor the atmosphere for mutagenicity during sugar cane harvesting season. Environ. Mol. Mutagen. 2008. © 2008 Wiley-Liss, Inc. [source] Pyrolysis studies of polyethylene terephthalate/silica nanocompositesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2007Jin Zheng Abstract The decomposition of pure polyethylene terephthalate (PET) and PET/silica nanocomposites was investigated by thermal gravimetry (TG) and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). The influence of the nanosized silica on the pyrolysis properties of the composites was found from the results that the activation energies of decomposition and the residual carbon content increase with silica nanoparticles. It is deduced that the increase of the activation energies and the residual carbon content result from the adsorption of the decomposed products on the surface of silica. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 2007 [source] INFLUENCE OF PULSED ELECTRIC FIELD ON SELENOCYSTEINE CONTENT IN SACCHAROMYCES CEREVISIAEJOURNAL OF FOOD BIOCHEMISTRY, Issue 6 2008URSZULA PANKIEWICZ ABSTRACT Culture of Saccharomyces cerevisiae with sodium selenite addition in medium was treated by pulsed electric fields (PEFs). Amino acids from yeast hydrolysates were separated by means of ion-exchange chromatography on amino acid analyzer according to previously established procedure. Selenocysteine was determined in a form of complex with ninhydrin, applying photometric technique. PEF treatment of S. cerevisiae cells resulted in about threefold content increase of selenium bonded within selenocysteine. PRACTICAL APPLICATIONS Se yeast is an attractive source of Se because of its low cost and its ability to act as a precursor for selenoprotein synthesis. Se yeast can be consumed as such and as a nutritional supplement. Another possibility is to use selenized yeast instead of conventional yeast for baking bread. Bread is generally low in Se, and hence the use of selenized yeast for this purpose could result in higher Se intakes because bread is a common product consumed by many individuals (Dumont et al. 2006). The presented way to enrich the baking yeast in selenium, namely selenomethionine, may be successfully applied in yeast production, because the studied method is a relatively simple, nontoxic and cheap technique for introducing macrocompounds into the yeast cells. Such enriched selenium yeast may be a valuable and safe source of selenium at diet supplementation. [source] Effects of intramuscular fat deposition on the beef traits of Japanese Black steers (Wagyu)ANIMAL SCIENCE JOURNAL, Issue 2 2007Yasuko UEDA ABSTRACT Effects of intramuscular fat deposition on the chemical composition, tenderness, and free amino acids (FAA) concentration of beef were studied using various classified carcasses of 21 Japanese Black (Wagyu) steers. The Beef Marbling Standard (BMS) No., judged on the market in 1998, and fat content, ranged from 2 to 10 and 4.8 to 39.0% in the M. longissimus thoracis, respectively. Moisture content was negatively correlated with the fat content (r =,0.98, P < 0.01). In contrast, protein content was relatively constant up to approximately 23% fat, corresponding to BMS No.4, and decreased as the fat content increased. Cooking loss was also constant up to approximately 28% fat, corresponding to BMS No.4, and markedly decreased with fat content increase. The beef in these cases were, however, classified into BMS No. around 9 and 11, respectively, according to the BMS model in 1988. A negative correlation was found between the shear-force value and the fat content (r =,0.83, P < 0.05). Most FAA concentrations on the wet weight of meat were correlated negatively with the fat content, except glutamine, and this negative relationship was still observed when the concentrations were recalculated on the basis of protein. These results indicate that higher marbling Wagyu beef (above approx. 23% fat) would have an extremely lower content of protein, which would partly explain the lower cooking loss and FAA with fat increase. In addition, some other reasons not relating to protein content (e.g. high fat content preventing the breakdown of protein to FAA) seem to explain the negative correlation between fat and FAA. [source] Biochemical, mechanical, and spectroscopic analyses of genetically engineered flax fibers producing bioplastic (poly-,-hydroxybutyrate)BIOTECHNOLOGY PROGRESS, Issue 5 2009Magdalena Wróbel-Kwiatkowska Abstract The interest in biofibers has grown in recent years due to their expanding range of applications in fields as diverse as biomedical science and the automotive industry. Their low production costs, biodegradability, physical properties, and perceived eco-friendliness allow for their extensive use as composite components, a role in which they could replace petroleum-based synthetic polymers. We performed biochemical, mechanical, and structural analyses of flax stems and fibers derived from field-grown transgenic flax enriched with PHB (poly-,-hydroxybutyrate). The analyses of the plant stems revealed an increase in the cellulose content and a decrease in the lignin and pectin contents relative to the control plants. However, the contents of the fibers' major components (cellulose, lignin, pectin) remain unchanged. An FT-IR study confirmed the results of the biochemical analyses of the flax fibers. However, the arrangement of the cellulose polymer in the transgenic fibers differed from that in the control, and a significant increase in the number of hydrogen bonds was detected. The mechanical properties of the transgenic flax stems were significantly improved, reflecting the cellulose content increase. However, the mechanical properties of the fibers did not change in comparison with the control, with the exception of the fibers from transgenic line M13. The generated transgenic flax plants, which produce both components of the flax/PHB composites (i.e., fibers and thermoplastic matrix in the same plant organ) are a source of an attractive and ecologically safe material for industry and medicine. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009 [source] Availability of polycyclic aromatic hydrocarbons from lampblack-impacted soils at former oil-gas plant sites in California, USAENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 3 2007Lei Hong Abstract Lampblack-impacted soils at former oil-gas plant sites in California, USA, were characterized to assess the sorption of polycyclic aromatic hydrocarbons (PAHs) and the concentration-dependent effects of a residual oil tar phase on sorption mechanism and availability of PAHs. Nuclear magnetic resonance spectroscopy demonstrated similar aromaticity for both lampblack carbon and the oil tar phase, with pronounced resonance signals in the range of 100 to 150 ppm. Scanning-electron microscopic images revealed a physically distinct oil tar phase, especially at high concentrations in lampblack, which resulted in an organic-like film structure when lampblack particles became saturated with the oil tar. Sorption experiments were conducted on a series of laboratory-prepared lampblack samples to systematically evaluate influences of an oil tar phase on PAH sorption to lampblack. Results indicate that the sorption of PAHs to lampblack exhibits a competition among sorption phases at low oil tar contents when micro- and mesopores are accessible. When the oil tar content increases to more than 5 to 10% by weight, this tar phase fills small pores, reduces surface area, and dominates PAH sorption on lampblack surface. A new PAH partitioning model, Kd = KLB-C(1- ftar)° + ftarKtar (, = empirical exponent), incorporates these effects in which the control of PAH partitioning transits from being dominated by sorption in lampblack (KLB-C) to absorption in oil tar (Ktar), depending on the fraction of tar (ftar). This study illustrates the importance of understanding interactions among PAHs, oil tar, and lampblack for explaining the differences in availability of PAHs among site soils and, consequently, for refining site-specific risk assessment and establishing soil cleanup levels. [source] Microstructure and Mechanical Properties of New AlCoxCrFeMo0.5Ni High-Entropy AlloysADVANCED ENGINEERING MATERIALS, Issue 1-2 2010Chin-You Hsu Effects of Co content on microstructures and hot hardness of a new high-entropy alloy system, AlCoxCrFeMo0.5Ni (x,=,0.5 to 2.0) were investigated. As cobalt content increases, the microstructure changes from dendrite to polygrain type and the constituent phases change from BCC,+,, at x,=,0.5 to BCC,+,FCC,+,, at x,=,2.0. The alloy hardness varies from Hv 788 at x,=,0.5 to Hv 596 at x,=,2.0. This can be explained with the relative amount of hard , phase, medium hard BCC phase and soft FCC phase. All the AlCoxCrFeMo0.5Ni alloys possess higher hardness level than that of Ni-based superalloys In 718/In 718 H from room temperature to 1273,K. They obey the Westbrook equation presenting the normal heating behavior. Both alloys of x,=,0.5 and 1.0 exhibit a transition temperature higher than that of Co-based alloy T-800 by about 200,K. They also have a high hot hardness of Hv 347 at 1273,K, which is higher than those of In 718 and In718 H by Hv 220. The strengthening mechanism for their superiority is proposed. The AlCoxCrFeMo0.5Ni alloy system has great potential in high-temperature applications. [source] Application of small-angle scattering to study the effects of moisture content on a native soy proteinJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 3 2008Catherine S. Kealley The nano- and microstructure of glycinin, a soybean protein, has been investigated as a function of moisture for moisture contents between 4 and 21,wt%. Glycinin exhibits peaks in the small-angle region whose positions show minimal change with X-rays for samples up to 13% moisture. However, the use of neutron scattering, and the associated enhancement in contrast, results in the Bragg peaks being well resolved up to higher moisture contents; the associated shift in peak positions between 4 and 21% moisture are consistent with the expansion of a hexagonal unit cell as a function of moisture content. A Porod slope of ,,4 indicates that the interface between the `dry' protein powder and the surrounding medium at a length-scale of at least 3,µm down to ,20,nm is smooth and sharp. Scanning electron microscopy indicates that the powders, with low moisture content, have a porous appearance, with the porosity decreasing and microstructure expanding as the moisture content increases. [source] Structure and properties of phase change materials based on HDPE, soft Fischer-Tropsch paraffin wax, and wood flourJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2010M. E. Mngomezulu Abstract Phase-change materials based on high density polyethylene (HDPE), soft Fischer-Tropsch paraffin wax (M3), and alkali-treated wood flour (WF) were investigated. The blend and composite samples were prepared by melt mixing using a Brabender Plastograph, followed by melt pressing. They were characterized in terms of their morphology, as well as thermal, mechanical, thermo-mechanical, and water absorption properties. Although SEM micrographs showed some evidence of intimate contact between the WF particles and the HDPE matrix as a result of alkali treatment, poor filler dispersion, and interfacial adhesion were also observed. Partial immiscibility of the HDPE and the M3 wax was noticed, with the WF particles covered by wax. There was plasticization of the HDPE matrix by the wax, as well as partial cocrystallization, inhomogeneity and uneven wax dispersion in the polymer matrix. The HDPE/WF/M3 wax composites were more homogeneous than the blends. The presence of wax reduced the thermal stability of the blends and composites. Both the presence of M3 wax and WF influenced the viscoelastic behavior of HDPE. The HDPE/M3 wax blends showed an increase in the interfacial amorphous content as the wax content increases, which resulted in the appearance of a ,-relaxation peak. The presence of M3 wax in HDPE reduced the mechanical properties of the blends. For the composites these properties varied with WF content. An increase in wax content resulted to a decrease in water uptake by the composites, probably because the wax covered the WF particles and penetrated the pores in these particles. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Thermal properties and phase morphology of melt-mixed poly(trimethylene terephthalate)/poly(hexamethylene isophthalamide) blendsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2008Fang-Chyou Chiu Abstract This work examines the thermal properties and phase morphology of melt-mixed poly(trimethylene terephthalate) (PTT)/poly(hexamethylene isophthalamide) (PA 6I) blends. Two temperatures, i.e., 250 and 260°C, are used to prepare the blends, respectively. Differential scanning calorimetry results indicate the immiscible feature of the blends. It is thus concluded that the ester-amide interchange reaction hardly occurred in the PTT/PA 6I blends. Depending on the composition and mixing temperature, the crystallization ability of PTT in the blends is either enhanced or hindered. Basically, a lower PA 6I content shifts the PTT melt crystallization to a higher temperature, whereas a higher PA 6I content causes an opposing outcome. The original complex melting behavior of neat PTT becomes more regular after the incorporation of 60 wt % or 80 wt % of PA 6I. Thermogravimetry analyses (TGA) show that the thermal stability of the blends improves as the PA 6I content increases. The two-phased morphology of the blends is examined by scanning electron microscopy (SEM). Polarized light microscopy (PLM) results reveal that the PTT spherulites become coarser with the inclusion of PA 6I; only smaller/dispersed crystallites are observed in the blend with 20 wt % of PTT. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Comparative study of the hydrolytic degradation of glycolide/L -lactide/,-caprolactone terpolymers initiated by zirconium(IV) acetylacetonate or stannous octoateJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2008Janusz Kasperczyk Abstract A series of copolymers have been synthesized by the ring-opening polymerization of glycolide, L -lactide, and ,-caprolactone with zirconium(IV) acetylacetonate [Zr(Acac)4] or stannous octoate [Sn(Oct)2] as the catalyst. The resulting terpolymers have been characterized by analytical techniques such as proton nuclear magnetic resonance, size exclusion chromatography, and differential scanning calorimetry. Data have confirmed that Sn(Oct)2 leads to less transesterification of polymer chains than Zr(Acac)4 under similar conditions. The various copolymers have been compression-molded and allowed to degrade in a pH 7.4 phosphate buffer at 37°C. The results show that the degradation rate depends not only on the copolymer composition but also on the chain microstructure, the Sn(Oct)2 -initiated copolymers degrading less rapidly than Zr(Acac)4 -initiated ones with more random chain structures. The caproyl component appears the most resistant to degradation as its content increases in almost all cases. Moreover, caproyl units exhibit a protecting effect on neighboring lactyl or glycolyl units. The glycolyl content exhibits different features: it decreases because of faster degradation of glycolyl units, which are more hydrophilic than caproyl and lactyl ones, remains stable in the case of abundant CGC sequences, which are very resistant to degradation, or even increases because of the formation of polyglycolide crystallites. Terpolymers can crystallize during degradation if the block length of one of the components is sufficiently long, even though they are amorphous initially. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Effect of ATH content on electrical and aging properties of EVA and silicone rubber blends for high voltage insulator compoundJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2007M. A. Pradeep Abstract The effect of trihydrated alumina (Al2O3, 3H2O) (ATH) filler in ethylene-vinyl acetate copolymer (EVA) and silicone rubber blends was investigated by performing a series of laboratory experiments to simulate different natural aging conditions. Samples with varying ATH content in a 50-50 blend of EVA and polydimethylsiloxane (PDMS) (silicone rubber, MQ) were tested to investigate the tracking resistance, resistance to UV radiation, corona, heat, and water immersion. Changes in surface resistivity, volume resistivity, and hydrophobic characteristics were evaluated for different compounds having ATH content. These exercises were mainly carried out to optimize the filler level. In immersed condition the water absorption increases with ATH content. The recovery of hydrophobicity, after aging by heat, is appreciable at higher ATH levels, than at lower ATH levels. The tracking and erosion resistance decrease as ATH content increases. When compounds containing different ATH content were subjected to corona treatment, the samples with higher ATH levels exhibited better results. All samples changed their color to a darker shade and there was an increase in the hydrophobicity, when subjected to UV radiation. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3505,3516, 2007 [source] Rheological properties of poly(methyl methacrylate)/rigid ladderlike polyphenylsilsesquioxane blendsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2007Guizhi Li Abstract A series of poly(methyl methacrylate) (PMMA) blends with rigid ladderlike polyphenylsilsesquioxane (PPSQ) were prepared at weight ratios of 100/0, 95/5, 90/10, 85/15, and 80/20 by solution casting and then hot-pressing. Their rheological properties have been studied under both dynamic shear and uniaxial elongation conditions. Their rheological properties depend on the compositions. The storage modulus, G,, loss modulus, G,, and dynamic shear viscosity, ,*, of the PMMA/PPSQ 95/5 blend were slightly lower than those of pure PMMA. However, the values of G,, G,, and ,* for the other PMMA/PPSQ blends are higher than those of PMMA. The G, values increase with an increase in PPSQ content from 5% through 15% PPSQ at low frequencies and then drop as the PPSQ content increases to 20%. Uniaxial elongational viscosity (,E) data demonstrate that PMMA/PPSQ blends exhibit slightly weaker (5% PPSQ) and much weaker (10% PPSQ) strain-hardening than PMMA. In contrast, the PMMA/PPSQ 85/15 blend shows strain-softening. Neither strain-hardening nor strain-softening was observed in the 80/20 blend. The special rheological properties for the 95/5 blend is probably due to a decrease in PMMA entanglements brought by the specific PMMA,PPSQ interactions. Rheological properties of PMMA/PPSQ blends with higher PPSQ content (,10%) are mainly affected by formation of hard PPSQ particles. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 352,359, 2007 [source] Electrochemical Behavior of Gel-Derived Lanthanum Calcium Cobalt Ferrite Cathode in Contact with LAMOX ElectrolyteJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2008Tsu-Yung Jin The electrochemical performance and structural features of (La1,yCay)(CoxFe1,x)O3 cathode prepared via a citrate acid gel route are studied when it is interfaced with the (La1.8Dy0.2)(Mo2,zWz)O9 electrolyte. The resistance and chemical capacitance of a low-frequency arc are extracted from the impedance results to evaluate its catalytic activity in oxygen reduction reaction (ORR). (La0.75Ca0.25)(Co0.8Fe0.2)O3 cathode exhibits the minimum area-specific resistance of 0.9 , cm2 and maximum capacitance of 5.7 mF/cm2 at 800°C among the compositions of x=0.1,0.9 and y=0.25. As the Co content increases, the decrease in resistance outweighs the increase in capacitance so that the product of resistance and capacitance (RC time constant) decreases. In contrast, when varying the Ca content of the A-site, the changes in resistance and the capacitance compensate each other; hence the RC time constant is virtually unchanged with respect to the calcium content. Thus, Co is a more influential element than Ca on the ORR catalytic activity. The pore structure study reveals a small amount of Mo diffuses from the electrolyte into the cathode, and its quantity is reduced when interfaced to an electrolyte of high W content. [source] Microwave Plasma Synthesis of Nanostructured ,-Al2O3 PowdersJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2003L. Fu Nanostructured Al2O3 powders have been synthesized by combustion of aluminum powder in a microwave oxygen plasma, and characterized by X-ray diffraction and electron microscopy. The main phase is ,-Al2O3, with a small amount of ,-Al2O3. The particles are truncated octahedral in shape, with mean particle sizes of 21,24 nm. The effect of reaction chamber pressure on the phase composition and the particle size was studied. The ,-alumina content increases and the mean particle size decreases with decreasing pressure. No ,-Al2O3 appears in the final particles. Electron microscopy studies find that a particle may contain more than one phase. [source] Synthesis and Characterization of Ethylene/Propylene Copolymers in the Whole Composition RangeMACROMOLECULAR SYMPOSIA, Issue 1 2007Ma. Joaquina Caballero Abstract Summary: The incorporation of comonomer molecules in the backbone of a homopolymer can influence the final properties of the material, decreasing its crystallinity and the melting and glass transition temperatures, and increasing its impact resistance and transparency. In the present work, ten ethylene/propylene copolymers have been synthesized using a supported metallocene catalytic system covering the whole composition range. Any desired composition was obtained by controlling the feed composition during the reaction. These synthesized copolymers have been characterized by different techniques in order to study the effect of the comonomer incorporation onto their final properties. When the comonomer content is low, the behaviour of the copolymer is similar to that of the corresponding homopolymer. Nevertheless, if the comonomer content increases, the copolymer becomes more amorphous (low crystallization temperature and soft XRD signals) and easily deformable, reaching a behaviour close to that corresponding to an elastomeric material. In order to corroborate these results the samples have been characterized by TREF and GPC-MALS. TREF analysis showed that copolymers containing less than 10% and more than 80% of ethylene are semicrystalline, with elution temperatures typical of this kind of polymers. Molecular weights are higher for homopolymers and they decrease as the comonomer concentration increases, whereas the polydispersity index keeps almost constant at the expected value for this kind of samples. [source] Effect of the oxygen nonstoichiometry on the structure and magnetic properties of Nd2CoMnO6+, double perovskitesPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 9 2007A. P. Sazonov Abstract The properties of Nd2CoMnO6+, (, up to 0.12) were investigated by means of neutron powder diffraction and magnetization measurements. It is found that the samples exhibit partial ordering of Co and Mn ions which strongly affects the magnetic properties. Ionic disorder increases with the oxygen content. According to neutron diffraction the stoichiometric and nonstoichiometric samples show ferromagnetic components which decreases as the oxygen content increases. The magnetization study of the strongly oxidized sample reveals a metamagnetic behavior. It is assumed that metamagnetism results from clusters with short-range antiferromagnetic order. Enhancement of the oxygen content leads to a conversion of Co2+ into low spin Co3+ and the appearance of a cationic vacancy which destroys the ionic order and stabilizes the overall antiferromagnetic behavior. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Theoretical investigations on anisotropic optical properties in semipolar and nonpolar InGaN quantum wellsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 9 2008Kazunobu Kojima Abstract The anisotropic band structures and spontaneous emission of the non c plane InGaN/GaN quantum wells (QWs) were computed based on the k·p perturbation theory. Spontaneous emission due to the A valence band is strongly polarized perpendicular to the c axis, while that from the B band has 90º-rotated polarization, for the crystal angle , larger than 50°. However, it was found that excited carriers can distribute into both the A and B bands, so that the effective polarization Peff defined by the integrated luminescence intensity is much reduced even for nonpolar InGaN/GaN QWs. Thus, Peff was systematically studied for arbitrary planes. We found that the energy separation between the A and B bands becomes significant and carrier population of the B valence band is suppressed as the In content increases, when Peff approaches unity. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] The role of abscisic acid and auxin in the response of poplar to abiotic stressPLANT BIOLOGY, Issue 2 2010J. Popko Abstract The plant hormones auxin and abscisic acid may at first sight appear to be a conflicting pair of plant regulators. Abscisic acid content increases during stress and protects plant water status. The content of free auxin in the developing xylem of poplar declines during stress, while auxin conjugates increase. This indicates that specific down-regulation of a signal transduction chain is important in plant adaptation to stress. Diminished auxin content may be a factor that adapts growth and wood development of poplar during adverse environmental conditions. To allow integration of environmental signals, abscisic acid and auxin must interact. Data are accumulating that abscisic acid,auxin cross-talk exists in plants. However, knowledge of the role of plant hormones in the response of trees to stress is scarce. Our data show that differences in the localisation of ABA synthesis exist between the annual, herbaceous plant Arabidopsis and the perennial woody species, poplar. [source] Dynamic mechanical properties and morphology of poly(benzyl methacrylate)/epoxy thermoset blendsPOLYMER ENGINEERING & SCIENCE, Issue 9 2010Margarita G. Prolongo Poly(benzyl methacrylate) (PBzMA)/epoxy thermoset blends of composition 5 to 25 wt% of PBzMA were prepared curing with 4,4,diaminodiphenylmethane (DDM), to study the influence of composition on the morphology and dynamic-mechanical properties of the blends. The cured blends are phase separated in PBzMA-rich phase and epoxy rich-phase. As the PBzMA content increases, the morphology evolves from nodular, to combined and to totally inverted. The analysis of the ,-mechanical relaxations indicates that the glass transition temperatures (Tg) of PBzMA and of epoxy in the blends are different from the neat polymers, this is related to a noncomplete phase separation on curing. The profiles of the loss modulus-temperature curves are correlated with the change in morphology that appears increasing the PBzMA content. The storage modulus-temperature curves are highly dependent on the morphology of the samples. The storage modulus-composition dependence is predicted using several models for two phase composites. POLYM. ENG. SCI., 50:1820,1830, 2010. © 2010 Society of Plastics Engineers [source] Compatibilizers based on polypropylene grafted with itaconic acid derivatives.POLYMER ENGINEERING & SCIENCE, Issue 4 2003Effect on polypropylene/polyethylene terephthalate blends New types of compatibilizers based on functionalized polypropylene (PP) were synthesized by radical melt grafting either with monomethyl itaconate or dimethyl itaconate. The effect of these new modified PP compounds were tested as compatibilizers in PP/polyethylene terephthalate (PET) blends. Blends with compositions 15/85 and 30/70 by weight of PP and PET were prepared in a single-screw extruder. Morphology of the compatibilized blends revealed a very fine and uniform dispersion of the PP phase as compared with that of noncompatibilized blends of the same composition, leading to improved adhesion between the two phases. Whereas dimethyl itaconate derived agent showed less activity, the monomethyl itaconate parent compound showed an increase of the impact resistance of PET in PP/PET blend. This was attributed to the hydrophilic nature of the monomethyl itaconate part of this compatibilizer. The tensile strength of PET in noncompatibilized blends gradually decreases as the PP content increases, while blends containing functionalized PP exhibited higher values. [source] Effects of epoxy content on dynamic mechanical behaviour of PEI-toughened dicyanate,novolac epoxy blendsPOLYMER INTERNATIONAL, Issue 9 2004Dr Baochun Guo Abstract By varying the cyanate/epoxy ratio, three polyetherimide(PEI)-modified bisphenol A dicyanate,novolac epoxy resin blends with different epoxy contents were prepared. The effects of epoxy content on the dynamic mechanical behaviour of those blends were investigated by dynamic mechanical thermal analysis. The results showed that the glass transition temperature of the cyanate,epoxy network (Tg1) in the modified blend decreases with epoxy content. When the epoxy content increases, both the width of the glass transition of the cyanate,epoxy network and its peak density are depressed substantially. Although the tangent delta peak value of PEI is basically independent of epoxy content, the Tg of PEI (Tg2) decreases with epoxy content. Tg1 is independent of the PEI loading. When Tg1 is lower than Tg2, however, the Tg1 in the blend with revised phase structure is substantially lower than other blends. Copyright © 2004 Society of Chemical Industry [source] Mass Transfer, Oxygen Isotopic Variation and Gold Precipitation in Epithermal System: A Case Study of the Hishikari Deposit, Southern Kyushu, JapanRESOURCE GEOLOGY, Issue 3 2002Naotatsu SHIKAZONO Abstract: Transportation of various kinds of elements occurred in wall rocks (Quaternary andesites) during the hydrothermal alteration accompanied by the Hishikari epithermal gold mineralization. For example, K2O and MgO contents of wall rocks decrease away from the gold-quartz veins, while (CaO+Na2O) content increases, and SiO2 content is variable near the veins. Hydrothermal alteration zoning and bulk compositional variations in wall rocks suggest that the mixing of hydrothermal solution and acidic groundwater took place an important role as the cause for the hydrothermal alteration and bulk compositional variations. The relationship between dissolved silica concentration and temperature of hydrothermal solution mixed with groundwater is obtained based on precipitation kinetics-fluid flow,mixing model, and the computed results are compared with the distribution of SiO2 minerals (quartz and cristobalite) in the hydrothermal alteration zones. This comparison suggests that the most reasonable flow rate of fluids migrating through hydrothermal alteration zones, and A/M (A: surface area of rocks interacting with fluid, M: mass of fluid) are estimated to be ca. 10 -4.2 m/sec, and ca. 0.10 m2/kg, respectively. The mixing of two fluids (hydrothermal solution and acidic groundwater) can also explain ,18O zoning in the altered country rocks, hydrothermal alteration zoning from K-feldspar through K-mica to kaolinite from the center (veins) to margin, and deposition of gold. [source] Hydrogenolysis of glycerol with FeCo macrocyclic complex bonded to Raney Nickel support under mild reaction conditionsTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 2 2010K. A. Anand Abstract The hydrogenolysis of dilute glycerol solution to 1,2-propanediol was studied in the presence of heterogeneous catalyst (FeCoL/Raney Nickel) having a heterodinuclear FeCo macrocyclic complex ionically bonded to Raney Nickel. Studies on the stability of the complex bonded to the support were carried out at different temperature as well as the effect of solvent to confirm that it was stable up to 600°C and 100,h of refluxing. In the hydrogenolysis of glycerol, the temperature has been varied from 165 to 220°C with an initial hydrogen pressure 0.35,MPa and the conversion increases from 1% to 36% with no gases evolving in this temperature range. The major product is 1,2-propanediol which is formed with 80% selectivity. The initial water content (20,60%) in the feed was also varied and it was found that the conversion and yield of 1,2-propanediol increases when the water content increases. Based on literature, a kinetic model was proposed and optimal rate constants determined using Genetic Algorithm (GA). On a étudié l'hydrogénolyse d'une solution diluée de glycérol solution en 1,2-propanediol, en présence d'un catalyseur hétérogène (FeCoL/nickel de Raney) ayant un complexe macrocyclique hétérodinucléaire de FeCo ioniquement lié au nickel de Raney. Des études sur la stabilité du complexe lié au soutien ont été effectuées à différentes températures et on a étudié aussi l'effet du solvant pour confirmer qu'il était stable jusqu'à 600 °C et 100 h de reflux. Dans l'hydrogénolyse du glycérol, la température variait de 165 à 220°C avec une pression initiale d'hydrogène de 0,35 MPa et la conversion augmente de 1% à to 36% sans évolution des gaz dans cet intervalle de température. Le produit majeur est le 1,2-propanediol, lequel est formé avec une sélectivité de 80%. Le contenu d'eau initial (20% à 60%) dans l'alimentation variait également et on a conclu que la conversion et le rendement de 1,2-propanediol augmentait avec les augmentations de contenu d'eau. En se basant sur la littérature, un modèle cinétique a été proposé et des constantes de taux optimal ont été déterminées en utilisant un algorithme génétique. [source] Physicochemical and electrochemical characterizations of organic montmorillonite (OMMT)/sulfonated poly(ether ether ketone) (SPEEK) composite membranesASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 1 2010R. Gosalawit Abstract Physicochemical and electrochemical properties of the organic montmorillonite (OMMT)/sulfonated poly(ether ether ketone) (SPEEK) composite membranes are considered for their use as proton conducting membranes. The paper presents the preparation and characterization of SPEEK and its composite membranes with OMMT as well as their comparison to the reference Nafion® 117 membrane. Water uptake and thermal property (Td1) are improved when the OMMT loading content increases. Methanol permeability decreases as OMMT loading content increases up to as high as 53% (5 wt% OMMT/SPEEK composite membrane). For proton conductivity, all membranes show improvement when the operating temperature increases from 25 to 90 °C. The proton conductivity at 100 °C of 3 wt% OMMT/SPEEK composite membrane (5.6 × 10,2 S/cm) is one order of magnitude higher than that of Nafion® 117 (2 × 10,3 S/cm). Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Investigation of the ultradrawing properties of gel spun fibers of ultra-high molecular weight polyethylene/carbon nanotube blendsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2008Jen-Taut Yeh Abstract The carbon nanotubes (CNTs) contents, ultrahigh-molecular-weight polyethylene (UHMWPE) concentrations and temperatures of UHMWPE, and CNTs added gel solutions exhibited significant influence on their rheological and spinning properties and the drawability of the corresponding UHMWPE/CNTs as-prepared fibers. Tremendously high shear viscosities (,s) of UHMWPE gel solutions were found as the temperatures reached 140°C, at which their ,s values approached the maximum. After adding CNTs, the ,s values of UHMWPE/CNTs gel solutions increase significantly and reach a maximum value as the CNTs contents increase up to a specific value. At each spinning temperature, the achievable draw ratios obtained for UHMWPE as-prepared fibers prepared near the optimum concentration are significantly higher than those of UHMWPE as-prepared fibers prepared at other concentrations. After addition of CNTs, the achievable draw ratios of UHMWPE/CNTs as-prepared fibers prepared near the optimum concentration improve consistently and reach a maximum value as their CNTs contents increase up to an optimum value. To understand these interesting drawing properties of the UHMWPE and UHMWPE/CNTs as-prepared fibers, the birefringence, thermal, morphological, and tensile properties of the as-prepared and drawn fibers were investigated. Possible mechanisms accounting for these interesting properties are proposed. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] | |||||||||||||||||||