Ethylene

Distribution by Scientific Domains

Kinds of Ethylene

  • exogenous ethylene

  • Terms modified by Ethylene

  • ethylene acetal
  • ethylene biosynthesis
  • ethylene bridge
  • ethylene complex
  • ethylene copolymer
  • ethylene copolymerization
  • ethylene diamine
  • ethylene diamine tetraacetic acid
  • ethylene dimethacrylate
  • ethylene evolution
  • ethylene glycol
  • ethylene glycol dimethacrylate
  • ethylene glycol intoxication
  • ethylene glycol solution
  • ethylene homopolymerization
  • ethylene imine
  • ethylene oxide
  • ethylene polymerisation
  • ethylene polymerization
  • ethylene polymerization reaction
  • ethylene pressure
  • ethylene production
  • ethylene propylene diene monomer
  • ethylene response
  • ethylene signaling
  • ethylene synthesis
  • ethylene terephthalate
  • ethylene treatment
  • ethylene unit
  • ethylene vinyl acetate
  • ethylene vinyl acetate copolymer
  • ethylene vinyl alcohol

  • Selected Abstracts


    Host and non-host pathogens elicit different jasmonate/ethylene responses in Arabidopsis

    THE PLANT JOURNAL, Issue 5 2004
    Laurent Zimmerli
    Summary Arabidopsis does not support the growth and asexual reproduction of the barley pathogen, Blumeria graminis f. sp. hordei Bgh). A majority of germlings fail to penetrate the epidermal cell wall and papillae. To gain additional insight into this interaction, we determined whether the salicylic acid (SA) or jasmonate (JA)/ethylene (ET) defence pathways played a role in blocking barley powdery mildew infections. Only the eds1 mutant and NahG transgenics supported a modest increase in penetration success by the barley powdery mildew. We also compared the global gene expression patterns of Arabidopsis inoculated with the non-host barley powdery mildew to those inoculated with a virulent, host powdery mildew, Erysiphe cichoracearum. Genes repressed by inoculations with non-host and host powdery mildews relative to non-inoculated control plants accounted for two-thirds of the differentially expressed genes. A majority of these genes encoded components of photosynthesis and general metabolism. Consistent with this observation, Arabidopsis growth was inhibited following inoculation with Bgh, suggesting a shift in resource allocation from growth to defence. A number of defence-associated genes were induced during both interactions. These genes likely are components of basal defence responses, which do not effectively block host powdery mildew infections. In addition, genes encoding defensins, anti-microbial peptides whose expression is under the control of the JA/ET signalling pathway, were induced exclusively by non-host pathogens. Ectopic activation of JA/ET signalling protected Arabidopsis against two biotrophic host pathogens. Taken together, these data suggest that biotrophic host pathogens must either suppress or fail to elicit the JA/ET signal transduction pathway. [source]


    Aminopyridinate-Stabilized Lanthanoid Complexes: Synthesis, Structure and Polymerization of Ethylene and Isoprene

    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 18 2010
    Christian Döring
    Abstract A series of aminopyridinate-stabilized dialkyl-lanthanoid complexes has been synthesized and characterized. The complexes were prepared by alkane elimination reacting [Ln(CH2SiMe3)3(thf)2] (Ln = Er, Yb, Lu) or [Ln(CH2Ph)3(thf)3] (Ln = Y, Er, Lu) with one equivalent of the bulky aminopyridine (2,6-diisopropylphenyl)-[6-(2,4,6-triisopropylphenyl)pyridin-2-yl]amine. Single-crystal X-ray analyses were carried out for all of the benzyl derivatives. The reaction of these compounds with ammonium borate leads to the elimination of one of the two alkyl functions and affords organolanthanoid cations. The aminopyridinate-stabilized dialkyl-lanthanoid compounds can initiate the polymerization of isoprene after activation with perfluorinated tetraphenyl borates. The obtained polymers have a 3,4-content of 60,95,%. The metal ion size as well as the addition of alkylaluminium compounds influences the microstructure of the obtained polymer. Aminopyridinate-stabilized organolanthanoid cations of Sc, Lu, Er and Y can polymerize ethylene in the presence of alkylaluminium compounds. The Lu, Er and Y complexes act as a CCTP catalyst and the erbium compound exhibits the highest activity. [source]


    Mono(aryloxido)Titanium(IV) Complexes and Their Application in the Selective Dimerization of Ethylene

    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 20 2009
    Jean-Benoit Cazaux
    Abstract We report on the synthesis of mono(aryloxido)titanium(IV) complexes of general formula {Ti[O(o -R)Ar]X3}, with X = OiPr, ArO = 2- tert -butyl-4-methylphenoxy and R = CMe3 (2a), CMe2Ph (2b) and CH2NMe2 (2c). Attempts to reach pure mono(aryloxido) complexes when R = CH2NMe(CH2Ph) (2d) or CH2N(CH2Ph)2 (2e) were unsuccessful. When R = CH2OMe, the analogous mononuclear complex was not obtained, and instead, a dinuclear complex [(2- tert -butyl-4-methyl-6-methoxymethylphenoxy) TiCl(OiPr)(,2 -OiPr)2TiCl(OiPr)2] (3) was formed. Complexes 2b and 3 were characterized by single-crystal X-ray diffraction. The former contains a tetrahedrally coordinated TiIV centre, whereas in the latter the aryloxido ligand behaves as a chelating,bridging ligand between the two, chemically very different metal centres that form two face-sharing octahedra. Different synthetic approaches starting from [Ti(OiPr)4] or [TiCl(OiPr)3] were evaluated and are discussed. The hemilabile behaviour of the aryloxido ligand resulting from reversible coordination of its side arm was studied by variable-temperature 1H NMR spectroscopy for 2c (R = CH2NMe2). Complexes 2a,d were contacted with ethylene and AlEt3 as cocatalyst. When activated with AlEt3 (3 equiv.) at 20 bar and 60 °C, complex 2c exhibits interesting activity (2100 g/gTi/h) for the selective dimerization of ethylene to 1-butene (92,% C4=; 99+% C4=1). Noticeable differences in catalyst activity were observed when the R group was modified. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]


    O -Acylated 2-Phosphanylphenol Derivatives , Useful Ligands in the Nickel-Catalyzed Polymerization of Ethylene

    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 9 2009
    Dmitry G. Yakhvarov
    Abstract The title ligands were prepared by O -acylation of 2-diphenylphosphanyl-4-methylphenol (1) or directly by double lithiation of 2-bromo-4-methylphenol and stepwise coupling with ClPPh2 and ClP(O)Ph2 or RC(O)Cl (R = Me, tBu, Ph, 4-MeOC6H4) to afford diphenylphosphinate 2 and carboxylic esters 3a,d. X-ray crystal structure analyses of 3b,d show conformations in which the P -phenyl substituents are rotated away from the ester group and the C(O)O , planes are nearly perpendicular to the phenol ring , plane. O -Acylated phosphanylphenols 2 and 3a,d form highly active catalysts with Ni(1,5-cod)2 (as does 1) for polymerization of ethylene, whereas phosphanylphenyl ethers do not give catalysts under the same conditions. The reason is the cleavage of the O -acyl bond upon heating with nickel(0) precursor compounds in the presence of ethylene. The precursors are P-coordinated Ni0 complexes, which are formed at room temperature, such as 4d obtained from 3d and Ni(cod)2 (in a 2:1 molar ratio), and characterized by multinuclear NMR spectroscopy. Upon heating in the presence of ethylene, the precatalysts are activated. Catalysts 2Ni and 3a,dNi convert ethylene nearly quantitatively, 2Ni slowly, and 3a,dNi rapidly, into linear polyethylene with vinyl and methyl end groups, and in the latter case, C(O)R end groups are also detectable. This proves insertion of Ni0 into the O,C(O)R bond of 3a,d ligands for formation of the primary catalyst. Termination of the first chain growing cycle by ,-hydride elimination changes the mechanism to the phosphanylphenolate,NiH initiated polymerization providing the main body of the polymer. A small retardation in the ethylene consumption rate with 3a,dNi catalysts relative to that observed for 1Ni and stabilization of the catalyst, which gives rise to reproducibly high ethylene conversion, is observed. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]


    Neutral and Cationic Methylaluminium Complexes of 2-Anilinotropone Ligands: Synthesis, Characterization, and Reactivity toward Ethylene

    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 6 2004
    Daniela Pappalardo
    Abstract Some new aluminium complexes bearing bidentate monoanionic 2-anilinotroponate ligands have been synthesized and characterized. Reaction of 2-(2,6-diisopropylanilino)tropone or 2-(perfluoroanilino)tropone with AlMe3 (1 equiv.) gave, by methane elimination, compounds [2-(2,6-diisopropylanilino)tropone]AlMe2 (1) and [2-(perfluoroanilino)tropone]AlMe2 (2), respectively, as yellow solids. Reaction of 1 with 1 equiv. of the ligand furnished, by protodealumination of a second Al,CH3 bond, the [2-(2,6-diisopropylanilino)tropone]2AlMe derivative 3. The structure of 3 has been determined by single-crystal X-ray diffraction, showing a five-coordinate aluminium atom with a distorted trigonal-bipyramidal geometry. Compounds 1 and 3 underwent methyl abstraction reactions with B(C6F5)3; the resulting cationic species was trapped in the presence of THF in dichloromethane solution. The reactivity of the synthesized compounds in ethylene polymerisation has also been explored. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source]


    Facile, Efficient Copolymerization of Ethylene with Bicyclic, Non-Conjugated Dienes by Titanium Complexes Bearing Bis(,-Enaminoketonato) Ligands

    ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 10 2009
    Jing-yu Liu
    Abstract Copolymerizations of ethylene with 5-vinyl-2-norbornene or 5-ethylidene-2-norbornene under the action of various titanium complexes bearing bis(,-enaminoketonato) chelate ligands of the type, [R1NC(R2)CHC(R3)O]2TiCl2 (1, R1=Ph, R2=CF3, R3=Ph; 2, R1=C6H4F- p, R2=CF3, R3=Ph; 3, R1=Ph, R2=CF3, R3=t- Bu; 4, R1=C6H4F- p, R2=CF3, R3=t- Bu; 5, R1=Ph, R2=CH3, R3=CF3; 6, R1=C6H4F- p, R2=CH3, R3=CF3), have been shown to occur with the regioselective insertion of the endocyclic double bond of the monomer into the copolymer chain, leaving the exocyclic vinyl double bond as a pendant unsaturation. The ligand modification strongly affects the copolymerization behaviour. High catalytic activities and efficient co-monomer incorporation can be easily obtained by optimizing the catalyst structures and polymerization conditions. [source]


    Compressive response and energy absorption of foam EPDM

    JOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2007
    Biqin Wang
    Abstract Ethylene,propylene,diene terpolymer foam was prepared by two different processing routes. The microstructure and mechanical properties of the foams with wide relative density ranging from 0.11 to 0.62 have been studied via scanning electron microscopy and mechanical testing, respectively. Scanning electron microscopy shows that the foam with lower relative density has a unique bimodal cell size structure, which the larger cells inlay among the smaller cells, while the foam articles with higher relative density have thicker cell walls with few small cells. The compressive stress,strain curves show that the foam articles with lower relative density have three regimes: linear elastic, a wide slightly rising plateau, and densification, while the foam articles with higher relative density have only two regimes: the longer linear elastic and densification. The relative modulus increases with the increase in the relative density. The contribution of the gas trapped in the cell to the modulus could be neglected. The energy absorbed per unit volume is relationship with the permitted stress and the relative density. The efficiency and the ideality parameter were evaluated from the compressive stress,strain plots. The parameters were plotted against stress to obtain maximum efficiency and the maximum ideality region, which can be used for optimizing the choice for practical applications in cushioning and packaging. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 [source]


    Comparative evaluation of 99mTc-ethylene bis-l-cysteine and 99mTc-ethylene bis-l-,-homocysteine during reversed phase HPLC analysis and electrophoresis at various pH conditions

    JOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 4 2001
    K.O. Mang'era
    Ethylene bis- L -,-homocysteine (L,L -EH) differs from ethylene bis- L -cysteine (L,L -EC) in having an extra methylene group between each pair of amine and carboxyl groups. The objective of this study was to determine the effect of the extra methylene groups on the characteristics of the complex of these compounds with technetium-99m during analysis by reversed phase HPLC and by electrophoresis at various pH values. Up to pH 5.5, 99mTc- L,L -EH exhibits a substantially longer retention time during reversed phase HPLC than 99mTc- L,L -EC, suggesting a more lipophilic character for 99mTc- L,L -EH under these conditions. On the other hand, 99mTc- L,L -EH clearly possesses a higher negative charge in the pH range 3-6.5 as shown by the markedly greater migration towards the anode in electrophoresis experiments. A rational explanation for these seemingly opposing observations can not yet be offered. Copyright © 2001 John Wiley & Sons, Ltd. [source]


    Characterization of a Novel RING Finger Gene OsRFP1, which is Induced by Ethylene, Salicylic Acid and Blast Fungus Infection in Rice

    JOURNAL OF PHYTOPATHOLOGY, Issue 7-8 2008
    Shanyue Zhou
    Abstract OsRFP1, a C3H2C3 -type zinc finger gene, was isolated through screening a blast-induced rice cDNA library. The full-length cDNA of the OsRFP1 gene is 1393 bp with an open reading frame (ORF) encoding 302 amino acid residues. The deduced amino acid sequence of OsRFP1 contains an N-terminal Pfam:zf-CHY domain and a C-terminal C3H2C3 -type RING signature. OsRFP1 was found localizing in the nucleus based on the fluorescence emitted by OsRFP1-GFP fusion protein expressed in onion epidermal cells. GAL4 DNA-binding vector pBD-containing OsRFP1 could activate expression of the reporter genes of His/Ade/LacZ in yeast strain AH109 indicating that OsRFP1 has the transcriptional activation activity. RNA blot analysis showed that expression of the OsRFP1 gene was significantly induced by ethylene (ET), salicylic acid (SA) and blast fungus infection. Together, these results indicate that the OsRFP1 may function as a transcriptional regulator in ET-dependent signal pathway in plant defense. [source]


    Elicitation of Ethylene by Verticillium albo-atrum Phytotoxins in Potato

    JOURNAL OF PHYTOPATHOLOGY, Issue 3 2005
    B. Mansoori
    Abstract Petioles from a susceptible cultivar (Désirèe) of Solanum tuberosum treated with a low-molecular mass toxin, separated from culture fluid of Verticillium albo-atrum, produced greater quantities of ethylene than did petioles of a tolerant cultivar (Home Guard). Pretreatment of leaflets from cv. Désirèe with silver thiosulphite, which inhibits perception of ethylene, prevented the chlorosis and necrosis normally associated with exposure to the toxin. Similarly, application of aminoethoxyvinylglycine (AVG) an inhibitor of aminocyclopropane-1-carboxylic acid (ACC) synthase, to petioles of cv. Désirèe reduced toxin-induced ethylene synthesis and symptom development. The data indicate that, in part, Verticillium -toxin acts through induction of ethylene biosynthesis in the host tissues, and different responses of susceptible and tolerant potato cultivars to V. albo-atrum are the result of differential production of ethylene. [source]


    Dual Role for Ethylene in Susceptibility of Tomato to Verticillium Wilt

    JOURNAL OF PHYTOPATHOLOGY, Issue 7-8 2001
    M. M. Robison
    Abstract Ethylene has been observed to both inhibit and promote the symptoms of Verticillium wilt (caused by Verticillium dahliae) in tomato. To test the hypothesis that ethylene has different effects at different stages in the infection process, ethylene levels were manipulated in V. dahliae -infected tomato plants by the application of an ethylene synthesis inhibitor aminoethoxyvinylglycine (AVG) and/or ethylene's biosynthetic precursor 1-aminocyclopropane-1-carboxylate (ACC) and the effects on disease severity were examined. Statistically significant reductions in disease severity were consistently obtained for AVG-treated plants that had ACC added at the time of inoculation. A model is therefore proposed in which post-infection ethylene enhances Verticillium wilt development in tomato whereas its presence at the time of infection inhibits disease development. [source]


    SERS-active sites on various copper substrates

    JOURNAL OF RAMAN SPECTROSCOPY, Issue 4 2001
    C. Siemes
    The wavenumbers of the Raman bands of ethylene adsorbed on Cu in ultra-high vacuum depend on the surface structure of the copper substrate. Thus it is possible to differentiate between ethylene adsorbed at Cu(110) sites, Cu(111) sites and surface defect sites of unknown configuration. These latter are the ,SERS-active sites.' Only when these sites are annealed does the distance dependence of SERS follow the expectations from the electromagnetic model of SERS. In the presence of the SERS-active sites, also the signal of ethylene at (111) sites shows a ,first layer effect.' Ethylene adsorbed on cold-deposited copper films shows strong infrared absorption at the same wavenumber as the ethylene at SERS-active sites in Raman scattering, irrespective of the Raman,infrared exclusion rule for the free centrosymmetric ethylene molecule. This raises the possibility that SERS-active sites are also infrared-active sites. The SERS-active sites at stepped Cu surfaces decorated by 3 nm of cold-deposited copper anneal below 200 K, whereas they prevail beyond 400 K on Cu island films. Copyright © 2001 John Wiley & Sons, Ltd. [source]


    Copolymerization of Ethylene with 2,7-Octadienyl Methyl Ether in the Presence of Metallocene and Nickel Diimine Catalysts

    MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 7 2009
    Mércia Fernandes
    Abstract In this work, copolymers of ethylene with 2,7-octadienyl methyl ether have been synthesized in the presence of three single-site catalysts. The obtained copolymers not only have a polar ether function but also a double bond in the side chains that is useful for secondary reactions. The polymers were characterized by GPC, EA, DSC, NMR, and FT-IR. The catalytic activity depends on the kind of catalysts, the concentration of the polar monomer, and the concentration of the protecting agent. Up to 7.3 wt.-% of MODE could be incorporated by the metallocene catalyst. These are in average 120 functional side groups in a polymer molecule with a molecular mass of 230,000. [source]


    Organoclay Nanocomposites from Ethylene,Acrylic Acid Copolymers

    MACROMOLECULAR MATERIALS & ENGINEERING, Issue 10 2006
    Sara Filippi
    Abstract Summary: A study of the structure,property relationships for nanocomposites prepared by melt compounding from ethylene,acrylic acid copolymers of varied composition and molecular architecture, and organoclays modified with different ammonium ions has been made by DSC, POM, SEM, TEM, WAXD, and rheological and mechanical tests. Within the series of clays investigated, the best levels of dispersion were displayed by those organically modified with quaternary ammonium ions containing two long alkyl tails. The relevant nanocomposites were shown to possess mixed exfoliated and intercalated morphology. The spacing of the intercalated clay stacks, most of which comprise few silicate layers, was found to be independent of clay loading, in the range of 2,50 phr, and to change with the molecular architecture of the matrix polymer. An indication that the excess surfactant present in some of the clays, and the organic material added in others to expand the interlayer spacing, were expelled from the clay galleries during melt blending and acted as plasticisers for the matrix polymer, was obtained from WAXD and rheological characterisations. TEM micrograph of the nanocomposite of EAA1 with 11 phr of 15A. [source]


    Ethylene and Propylene Polymerization Using In Situ Supported Me2Si(Ind)2ZrCl2 Catalyst: Experimental and Theoretical Study

    MACROMOLECULAR MATERIALS & ENGINEERING, Issue 3 2006
    Fernando C. Franceschini
    Abstract Summary: Me2Si(Ind)2ZrCl2 was in situ immobilized onto SMAO and used for ethylene and propylene polymerization in the presence of TEA or TIBA as cocatalyst. The catalytic system Me2Si(Ind)2ZrCl2/SMAO exhibited different behavior depending on the amount and nature of the alkylaluminum employed and on the monomer type. The catalyst activity was nearly 0.4 kg polymer,·,g cat,1,·,h,1 with both cocatalysts for propylene polymerization. Similar activities were observed for ethylene polymerization in the presence of TIBA. When ethylene was polymerized using TEA at an Al/Zr molar ratio of 250, the activity was 10 times higher. Polyethylenes made by in situ supported or homogeneous catalyst systems had practically the same melting point (Tm). On the other hand, poly(propylenes) made using in situ supported catalyst systems had a slightly lower Tm than poly(propylenes) made using homogeneous catalyst systems. The nature and amount of the alkylaluminum also influenced the molar mass. The poly(propylene) molar mass was higher when TIBA was the cocatalyst. The opposite behavior was observed for the polyethylenes. Concerning the alkylaluminum concentration, the molar mass of the polymers decreased as the amount of TEA increased. In the presence of TIBA, the polyethylene's molar mass was almost the same, independent of the alkylaluminum concentration, and the poly(propylene) molar mass increased with increasing amounts of cocatalyst. The deconvolution of the GPC curves showed 2 peaks for the homogeneous system and 3 peaks for the heterogeneous in situ supported system. The only exception was observed when TEA was used at an Al/Zr molar ratio of 500, where the best fit was obtained with 2 peaks. Based on the GPC deconvolution results and on the theoretical modeling, a proposal for the active site structure was made. Molar mass distribution deconvolution of polyethylene prepared with the system Me2Si(Ind)2ZrCl2/SMAO/TIBA with 500 mol/mol of alkylaluminum as cocatalyst. [source]


    Silyl-Terminated Ethylene- co -Norbornene Copolymers by Organotitanium-Based Catalysts

    MACROMOLECULAR RAPID COMMUNICATIONS, Issue 1 2009
    Roberto Marconi
    Abstract Ethylene (E) and norbornene (N) were copolymerized in the presence of PhSiH3 as chain-transfer agent with [Ti(,5:,1 -C5Me4SiMe2NBut)(,1 -Me)2] precatalyst combined with [Ph3C][B(C6F5)4]. The silane was introduced at chain-ends of E- co -N copolymers with concomitant reinitiation of the growing polymer chain. The concentrations of the silane and polymer molecular weight are inversely correlated. The characteristic signals of SiH2Ph chain-ends were observed by 1H NMR. The Si heteroatom is predominantly adjacent to ethylene units in E- co -N copolymers with high N content. [source]


    High-Pressure Polymerization of Ethylene in Tubular Reactors: A Rigorous Dynamic Model Able to Predict the Full Molecular Weight Distribution

    MACROMOLECULAR REACTION ENGINEERING, Issue 7 2009
    Mariano Asteasuain
    Abstract A rigorous dynamic model of the high-pressure polymerization of ethylene in tubular reactors is presented. The model is capable of predicting the full molecular weight distribution (MWD), average branching indexes, monomer conversion and average molecular weights as function of time and reactor length. The probability generating function method is applied to model the MWD. This technique allows easy and efficient calculation of the MWD, in spite of the complex mathematical description of the process. The reactor model is used to analyze the dynamic responses of MWD and other process variables under different transition policies, as well as to predict the effects of process perturbations. The influence of the material recycle on the process dynamics is also shown. [source]


    Sorption and Diffusion of Propylene and Ethylene in Heterophasic Polypropylene Copolymers

    MACROMOLECULAR SYMPOSIA, Issue 1 2007
    Michael Bartke
    Abstract Summary: Sorption experiments of ethylene and propylene in different polypropylene powder samples, both homopolymer and heterophasic copolymers with different rubber content, have been carried out in a high-pressure magnetic suspension balance at 10 bars pressure and 70,°C. The gross solubilities measured can be well correlated with the rubber content of the polymer samples. Solubility of ethylene and propylene in the rubber phase differ from solubility in the amorphous fraction of the homopolymer, especially the concentration ratio of propylene to ethylene differs significantly between rubber phase and amorphous fraction of the homopolymer. From the slope of monomer uptake, information on kinetics of mass-transfer can be gained. No significant differences were observed in terms of mass-transfer for ethylene and propylene. With increasing rubber content, effective diffusion coefficients increased slightly. By combined sorption studies with powder samples and compressed films, information about both effective diffusion coefficients and the effective length scale of diffusion could be gained. It could be shown, that the particle radius is not the characteristic length of diffusion in the studied powder samples. Mass transfer of nearly all samples could be described by a constant diffusion length of 120 to 130 µm, independently on particle size. This indicates that the effective scale of diffusion in polymer particles is in between microparticle and macroparticle scale used in classical particle modeling. [source]


    Ethylene , a key arbitrator to plant,fungal symbiotic interactions?

    NEW PHYTOLOGIST, Issue 4 2010
    Jonathan M. Plett
    First page of article [source]


    Effect of the combined treatment of insecticides and an attractant for the control of Phloeotribus scarabaeoides, a pest of Olea europea

    PEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 3 2003
    Estefanía Rodríguez
    Abstract Different insecticides have been tested for the control of the olive bark beetle, Phloeotribus scarabaeoides Bern. This scolytid can be managed at two points in its biological cycle: in pruned logs, where it excavates reproduction galleries, or in living trees, after emergence from the logs, where it digs feeding galleries. In mortality laboratory bioassays, the efficiency of organophosphorus insecticides has been ranked as follows: chlorpyrifos,+,dimethoate,<,formothion,<,methidathion. Formothion and methidathion, the two most efficient, were sprayed on olive logs together with a pyrethroid insecticide, deltamethrin, and a formulation which combined an organophosphorus (fenitrothion) and a pyrethroid (cypermethrin) insecticide. Deltamethrin inhibited the excavation of new reproduction galleries and induced a repellent effect on the olive pest. In contrast, none of the organophosphorus insecticides or the combination, fenitrothion,+,cypermethrin, were able to control the olive bark beetle. In olive trees, deltamethrin controlled this olive pest without showing the repellent effect observed for logs. Ethylene, a plant hormone, has been reported as an attractant for the olive bark beetle. The use of dispensers which released ethylene increased the number of P scarabaeoides approaching the treated olive trees, thus favouring its use in a lure-and-trap control system. © 2003 Society of Chemical Industry [source]


    A Study of the Interaction between Auxin and Ethylene in Wild Type and Transgenic Ethylene-Insensitive Tobacco during Adventitious Root Formation Induced by Stagnant Root Zone Conditions

    PLANT BIOLOGY, Issue 5 2003
    M. P. McDonald
    Abstract: Wild type (Wt) and transgenic plants (etr1-1 gene from Arabidopsis thaliana; encoding for a defective ethylene receptor; Tetr) of Nicotiana tabacum L. were subjected to experiments to resolve the role of the interaction between ethylene and auxin in waterlogging-induced adventitious root formation. Plants were grown in aerated or stagnant deoxygenated nutrient solution and treated with the following plant growth regulators: ethylene, the synthetic auxins 2,4-dichlorophenoxyacetic acid (2,4-D) and 1-naphthaleneacetic acid (1-NAA), and the auxin efflux inhibitor naphthylphthalamic acid (NPA). The superior growth of Wt in stagnant solution suggests that the ability to sense and respond to ethylene partially mediates tolerance to stagnant root zone conditions. Wt produced around 2 - 2.5-fold more adventitious roots than Tetr in aerated and stagnant solution. Treatment with NPA phenocopied the effects of ethylene insensitivity by reducing the number of adventitious roots on Wt to Tetr levels. Additionally, application of 1-NAA to the shoot of Tetr increased the number of adventitious roots on Tetr to similar levels as the untreated Wt. However, this level was only around half the number achieved by 1-NAA-treated Wt. The results suggest an interplay between ethylene and auxin in the process of adventitious root formation in waterlogged tobacco, most likely on the level of polar auxin transport. However, a separate non-auxin-related role as a transcription regulator for genes essential to adventitious root formation cannot be excluded. [source]


    Oxygen control of ethylene biosynthesis during seed development in Arabidopsis thaliana (L.) Heynh

    PLANT CELL & ENVIRONMENT, Issue 6 2002
    K. M. Ramonell
    Abstract An unforeseen side-effect on plant growth in reduced oxygen is the loss of seed production at concentrations around 25% atmospheric (50 mmol mol,1 O2). In this study, the model plant Arabidopsis thaliana (L.) Heynh. cv. ,Columbia' was used to investigate the effect of low oxygen on ethylene biosynthesis during seed development. Plants were grown in a range of oxygen concentrations (210 [equal to ambient], 160, 100, 50 and 25 mmol mol,1) with 0·35 mmol mol,1 CO2 in N2. Ethylene in full-sized siliques was sampled using gas chromatography, and viable seed production was determined at maturity. Molecular analysis of ethylene biosynthesis was accomplished using cDNAs encoding 1-aminocyclopropane -1-carboxylic acid (ACC) synthase and ACC oxidase in ribonuclease protection assays and in situ hybridizations. No ethylene was detected in siliques from plants grown at 50 and 25 mmol mol,1 O2. At the same time, silique ACC oxidase mRNA increased three-fold comparing plants grown under the lowest oxygen with ambient controls, whereas ACC synthase mRNA was unaffected. As O2 decreased, tissue-specific patterning of ACC oxidase and ACC synthase gene expression shifted from the embryo to the silique wall. These data demonstrate how low O2 modulates the activity and expression of the ethylene biosynthetic pathway during seed development in Arabidopsis. [source]


    Genetic dissection of the role of ethylene in regulating auxin-dependent lateral and adventitious root formation in tomato

    THE PLANT JOURNAL, Issue 1 2010
    Sangeeta Negi
    Summary In this study we investigated the role of ethylene in the formation of lateral and adventitious roots in tomato (Solanum lycopersicum) using mutants isolated for altered ethylene signaling and fruit ripening. Mutations that block ethylene responses and delay ripening ,Nr (Never ripe), gr (green ripe), nor (non ripening), and rin (ripening inhibitor) , have enhanced lateral root formation. In contrast, the epi (epinastic) mutant, which has elevated ethylene and constitutive ethylene signaling in some tissues, or treatment with the ethylene precursor 1-aminocyclopropane carboxylic acid (ACC), reduces lateral root formation. Treatment with ACC inhibits the initiation and elongation of lateral roots, except in the Nr genotype. Root basipetal and acropetal indole-3-acetic acid (IAA) transport increase with ACC treatments or in the epi mutant, while in the Nr mutant there is less auxin transport than in the wild type and transport is insensitive to ACC. In contrast, the process of adventitious root formation shows the opposite response to ethylene, with ACC treatment and the epi mutation increasing adventitious root formation and the Nr mutation reducing the number of adventitious roots. In hypocotyls, ACC treatment negatively regulated IAA transport while the Nr mutant showed increased IAA transport in hypocotyls. Ethylene significantly reduces free IAA content in roots, but only subtly changes free IAA content in tomato hypocotyls. These results indicate a negative role for ethylene in lateral root formation and a positive role in adventitious root formation with modulation of auxin transport as a central point of ethylene,auxin crosstalk. [source]


    Ethylene regulates lateral root formation and auxin transport in Arabidopsis thaliana

    THE PLANT JOURNAL, Issue 2 2008
    Sangeeta Negi
    Summary Lateral root branching is a genetically defined and environmentally regulated process. Auxin is required for lateral root formation, and mutants that are altered in auxin synthesis, transport or signaling often have lateral root defects. Crosstalk between auxin and ethylene in root elongation has been demonstrated, but interactions between these hormones in the regulation of Arabidopsis lateral root formation are not well characterized. This study utilized Arabidopsis mutants altered in ethylene signaling and synthesis to explore the role of ethylene in lateral root formation. We find that enhanced ethylene synthesis or signaling, through the eto1-1 and ctr1-1 mutations, or through the application of 1-aminocyclopropane-1-carboxylic acid (ACC), negatively impacts lateral root formation, and is reversible by treatment with the ethylene antagonist, silver nitrate. In contrast, mutations that block ethylene responses, etr1-3 and ein2-5, enhance root formation and render it insensitive to the effect of ACC, even though these mutants have reduced root elongation at high ACC doses. ACC treatments or the eto1-1 mutation significantly enhance radiolabeled indole-3-acetic acid (IAA) transport in both the acropetal and the basipetal directions. ein2-5 and etr1-3 have less acropetal IAA transport, and transport is no longer regulated by ACC. DR5-GUS reporter expression is also altered by ACC treatment, which is consistent with transport differences. The aux1-7 mutant, which has a defect in an IAA influx protein, is insensitive to the ethylene inhibition of root formation. aux1-7 also has ACC-insensitive acropetal and basipetal IAA transport, as well as altered DR5-GUS expression, which is consistent with ethylene altering AUX1-mediated IAA uptake, and thereby blocking lateral root formation. [source]


    The Bicorannulenyl Dianion: A Charged Overcrowded Ethylene,

    ANGEWANDTE CHEMIE, Issue 41 2010
    David Eisenberg
    Bicorannulenyl, ein großes Biaryl bestehend aus zwei ,schüsselförmigen" Corannulenen, wird nach Reduktion zum Dianion in ein sterisch überfrachtetes Ethylen umgewandelt (siehe Bild). DFT-Rechnungen und NMR-spektroskopische Untersuchungen lassen den Doppelbindungscharakter der zentralen Bindung zwischen den beiden Untereinheiten erkennen. Drei stabile Diastereomere, die sich durch Inversion und Rotation um die zentrale Bindung ineinander umwandeln lassen, wurden gefunden. [source]


    [O,NSR]TiCl3 -Catalyzed Copolymerization of Ethylene with Functionalized Olefins,

    ANGEWANDTE CHEMIE, Issue 43 2009
    Xiao-Hong Yang
    Wie am Schnürchen: Titankomplexe wurden als effiziente Katalysatoren für die Copolymerisation von Ethen mit polaren Olefinen, zum Beispiel ,-Alkenolen und ,-Alkensäuren, entwickelt. Auf diese Weise lässt sich ein Organophosphankatalysator an Polyethylen anknüpfen (siehe Bild; FG=funktionelle Gruppe, MMAO=modifiziertes Methylaluminoxan), um einen wiederverwertbaren Initiator der [3+2]-Cycloaddition zu erhalten. [source]


    Biphasic oligomerization of ethylene with nickel complexes immobilized in organochloroaluminate ionic liquids

    APPLIED ORGANOMETALLIC CHEMISTRY, Issue 11 2009
    Lixia Pei
    Abstract Ethylene was selectively oligomerized by nickel complexes such as (PPh3)2NiBr2 and (PPh3)2NiCl2 immobilized in chloroaluminate ionic liquid in biphasic catalytic reactions. The influence of reaction parameters such as reaction media, reaction temperature and Et2AlCl:Ni molar ratio was also evaluated. Turnover frequency up to 24000 mol C2H4/(mol Ni h) was achieved under mild reaction conditions (0.5 atm and 40 °C). GC-MS analyses showed that the obtained oligomers completely consist of C4 and C6. The olefinic products can be easily separated from the catalytic ionic liquid phase by simple decantation, and the nickel catalyst can be reused without a significant decrease in turnover frequency and change of the distribution of the olefinic products. Copyright © 2009 John Wiley & Sons, Ltd. [source]


    Ethylene and propylene polymerization by the new substituted bridged (cyclopentadienyl)(fluorenyl) zirconocenes

    APPLIED ORGANOMETALLIC CHEMISTRY, Issue 2 2006
    Xiaoxia Yang
    Abstract Eight Cs -symmetric complexes, R1R2C(Cp)(Flu)MCl2 [R1 = R2 = CH3CH2CH2, M = Zr (1), Hf (2); R1 = R2 = pCH3OC6H4, M = Zr (3), Hf (4); R1 = ptBuC6H4, R2 = Ph, M = Zr (5), Hf (6); R1 = R2 = ptBuC6H4, M = Zr (7); R1 = R2 = PhCH2, M = Zr (8)] have been synthesized and characterized. Zirconocenes all showed the same high catalytic activities in ethylene polymerization as complex Ph2C(Cp)(Flu)ZrCl2 (9). However, in the propylene polymerization, the catalytic activities decreased in the order 5 , 9 > 7 > 8. Introduction of tBu decreased the activities, probably due to the bulk steric hindrance. The polypropylene produced by 5 and 7 with tBu substituent showed a higher molecular weight (M,) than that produced by 9. The 13C NMR spectrum revealed the polymers from 7 and 8 to have shorter average syndiotactic block length than polymer produced by 9. It was noted that [mm] stereodefect of polypropylene by 8 could not be observed from 13C NMR, which showed that the benzyl on bridge carbon 8 prevented chain epimerization and enatiofacial misinsertion in polymerization. Copyright © 2005 John Wiley & Sons, Ltd. [source]


    Reactor Modeling of Gas-Phase Polymerization of Ethylene

    CHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 11 2004
    A. Kiashemshaki
    Abstract A model is developed for evaluating the performance of industrial-scale gas-phase polyethylene production reactors. This model is able to predict the properties of the produced polymer for both linear low-density and high-density polyethylene grades. A pseudo-homogeneous state was assumed in the fluidized bed reactor based on negligible heat and mass transfer resistances between the bubble and emulsion phases. The nonideal flow pattern in the fluidized bed reactor was described by the tanks-in-series model based on the information obtained in the literature. The kinetic model used in this work allows to predict the properties of the produced polymer. The presented model was compared with the actual data in terms of melt index and density and it was shown that there is a good agreement between the actual and calculated properties of the polymer. New correlations were developed to predict the melt index and density of polyethylene based on the operating conditions of the reactor and composition of the reactants in feed. [source]


    ChemInform Abstract: Ionic Liquids as Solvents for a Ruthenium-Catalyzed C,H Activation Reaction: Synthesis of Heterocyclic Compounds from ,,,-Unsaturated Imines, Carbon Monoxide, and Ethylene.

    CHEMINFORM, Issue 36 2010
    Tobias Biletzki
    Abstract The influence of reaction conditions (ionic liquid, pressure, temperature, time) on outcome and product ratio is studied. [source]