860 resultados para ethylene-propylene terpolymer (EPDM)
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Involvement of ethylene in the etiology of tomato plants (Lycopersicon esculentum) infected with the root-knot nematode (Meloidogyne incognita) was investigated. Endogenous root concentrations of ethylene were not significantly different in uninfected resistant var. Anahu and susceptible var. Vendor plants. Exposure of resistant plants to high doses of infectious nematode larvae did not affect root ethylene concentrations during the subsequent 30 day period. The possibility that ethylene may be involved in the mechanism of resistance is therefore not supported by these experiments. In no experiments did ethylene concentrations in roots of susceptible plants increase significantly subsequent to ~ incognita infestation. This result is not consistent with the hypothesis in the literature which suggests that increased ethylene production accompanies gall formation. Growth of susceptible tomato plants was affected by ~ incognita infestation such that root weights increased (due to galling), stem heights decreased and top weights increased. The possibility that alterations in stem growth resulted from increased production of 'stress' ethylene is discussed. Growth of resistant plants was unaffected by exposure to high doses of ~ incognita and galls were never detected on the roots of these plants. Root ethane concentrations generally varied in parallel with root ethylene concentrations although ethane concentrations were without exception greater. In 4 of 6 experiments conducted ethane/ethylene ratios increased significantly with time. These results are discussed in the light of published data on the relationship between ethane and ethylene synthesis. The term infested is used throughout this thesis in reference to plants whose root systems had been exposed to nematodes and does not distinguish between the susceptible and resistant response.
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Boron tribalide complexes of 1,1-bis(dimethylamino)ethylene (DME) , t etramethylurea (TMU), tetramethylguanidine (TMG) , and pentamethylguanidine (PMG) and also mixed boron t r ihalide adducts of DME have been investigated by 1H and 19F NMR spectroscopy. Both nitrogen and the C-Q-H carbon of DME are possible donor a toms to boron trihal ides but complexation has been found to occur only at carbon of DME. The initial adduct acts as a Bronsted acid and gives up a proton to free DME in solut ion. A side reaction in the DME-BF, system gives rise to trace amounts of a complex aSSigned as (DME)2BF2+. (DME)2BF2+ is produced in much larger quantities in t he DME-BF3-BC13 and DME-BF,-BBr, systems by reaction of free DME with DME:BF2X (X = Cl, Br). Restricted r otation about the C-N bonds of TMUlBC13 and n1U:BBr3 has been observed at low temperatures. This complements previous work in this system and confirms oxygen donation of TMU to boron trihalides . Restricted rotation at low temperatures also has been observed in DMEboron trihalide systems
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Les travaux de recherche prsents ici avaient pour objectif principal la synthse de copolymres statistiques base dthylne et dacide acrylique (AA). Pour cela, la dprotection des groupements esters dun copolymre statistique prcurseur, le poly(thylne-co-(tert-butyl)acrylate), a t effectue par hydrolyse laide diodure de trimthylsilyle. La synthse de ce prcurseur est ralise par polymrisation catalytique en prsence dun systme base de Palladium (Pd). Le deuxime objectif a t dtudier et de caractriser des polymres synthtiss ltat solide et en suspension collodale. Plusieurs copolymres prcurseurs comprenant diffrents pourcentages molaires en tert-butyl acrylate (4 12% molaires) ont t synthtiss avec succs, puis dprotgs par hydrolyse pour obtenir des poly(thylne-coacide acrylique) (pE-co-AA) avec diffrentes compositions. Seuls les copolymres comprenant 10% molaire ou plus de AA sont solubles dans le Ttrahydrofurane (THF) et uniquement dans ce solvant. De telles solutions peuvent tre dialyses dans leau, ce qui conduit un change lent entre cette dernire et le THF, et lautoassemblage du copolymre dans leau peut ensuite tre tudi. Cest ainsi quont pu tre observes des nanoparticules stables dans le temps dont le comportement est sensible au pH et la temprature. Les polymres synthtiss ont t caractriss par Rsonance Magntique Nuclaire (RMN) ainsi que par spectroscopie Infra-Rouge (IR), avant et aprs dprotection. Les pourcentages molaires dAA ont t dtermins par combinaison des rsultats de RMN et ii de titrages conductimtriques. A ltat solide, les chantillons ont t analyss par Calorimtrie diffrentielle balayage (DSC) et par Diffraction des rayons X. Les solutions collodales des polymres pE-co-AA ont t caractrises par Diffusion dynamique de la lumire et par la DSC-haute sensibilit. De la microscopie lectronique transmission (TEM) a permis de visualiser la forme et la taille des nanoparticules.
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Thse numrise par la Division de la gestion de documents et des archives de l'Universit de Montral
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Mmoire numris par la Division de la gestion de documents et des archives de l'Universit de Montral
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We have investigated the crystallization characteristics of melt compounded nanocomposites of poly(ethylene terephthalate) (PET) and single walled carbon nanotubes (SWNTs). Differential scanning calorimetry studies showed that SWNTs at weight fractions as low as 0.03 wt% enhance the rate of crystallization in PET, as the cooling nanocomposite melt crystallizes at a temperature 10 C higher as compared to neat PET. Isothermal crystallization studies also revealed that SWNTs significantly accelerate the crystallization process. WAXD showed oriented crystallization of PET induced by oriented SWNTs in a randomized PET melt, indicating the role of SWNTs as nucleating sites.
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Attempts have been made to attain satisfactory network structures in each of the phases of a rubber blend by minimising the cure rate imbalance by employing methods such as grafting of accelerators to the slow curing rubber, chemically bonding the crosslinking agents to the rubber in which it has lower solubility, functionalisation of the slow curing rubber, masterbatching of the curing agents to the slow curing rubber etc. Functionalisation of the slow curing constituents of NR/IIR and NR/EIPDM blends is tried using novel reagents as the first part of this study. However, the crux of the present study is a more direct approach to attaining a covulcanized state in NR/IIR and NR/EPDM blends: Precuring the slow curing rubber (IIR or EPDM) to a low level when it can still blend with NR and then to ck) the final curing after blending with NR. TNM3 precuring is also likely to minimise the viscosity mismatch. Since a low level of resmmal crosslink density is likely to be present lJ1 reclaimed rubbers, blending heat resistant reclaimed rubber such as butyl reclaim with NR may also have the same effect of precuring IIR, and then blending with NR. Hence use of IIR reclaim for developing blends with NR is also proposed to be investigated in this study
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Our new simple method for calculating accurate Franck-Condon factors including nondiagonal (i.e., mode-mode) anharmonic coupling is used to simulate the C2H4+X2B 3uC2H4X1 Ag band in the photoelectron spectrum. An improved vibrational basis set truncation algorithm, which permits very efficient computations, is employed. Because the torsional mode is highly anharmonic it is separated from the other modes and treated exactly. All other modes are treated through the second-order perturbation theory. The perturbation-theory corrections are significant and lead to a good agreement with experiment, although the separability assumption for torsion causes the C2 D4 results to be not as good as those for C2 H4. A variational formulation to overcome this circumstance, and deal with large anharmonicities in general, is suggested
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Rotational structure has been resolved and analyzed in two of the infraredactive perpendicular bands of C2H4 vapor: the Type b fundamental band, 10, at 826 cm1, and the Type c fundamental band, 7, at 949 cm1. Many of the individual PP and RR branch lines have been observed. The analysis has been confined to values of the quantum number K3, for which energy levels ethylene shows no detectable deviations from a symmetrictop rotational structure. The analysis reveals a Coriolis interaction between 7 and 10, and between 4 and 10, and values of the Coriolis constants 7,10z and 4,10y are obtained; these are related to normal coordinate calculations for the appropriate symmetry species, and force constants are derived to fit the observed zeta constants. The band center of 10 has been revised from the original figure of 810 cm1 to the new value, 826 cm1, and the inactive frequency 4 is estimated to lie at 10233 cm1, in good agreement with the previous estimate of 1027 cm1. The change in the value of 10 leads to a suggested change in the value of the Ramanactive fundamental 6 from 1236 to 1222 cm1. New combination bands have been observed at 2174 cm1, assigned as 3+10; and at 2252 cm1, assigned as 4+6; also rotational structure has been resolved and analyzed in the 6+10 band at 2048 cm1. The new data obtained for the C2H4 molecule are summarized in Table XII, with all of the other data presently available on the vibrational and rotational constants.
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Absolute intensity measurements have been made on the fundamental vibrations of ethylene and four of its deuteroisotopes. The bands were pressure broadened with nitrogen at 50 atmos, and the intensities were determined by the method of Wilson and Wells except that the observed optical density was integrated against logv rather than v. Normal coordinates have been calculated, and the intensities have been interpreted in terms of quantities (p/Si) giving the change in dipole moment with respect to each internal symmetry coordinate. Data from the different isotopic species have been used to eliminate ambiguities in the interpretation. Effective bond moments are calculated for each symmetry coordinate.
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Carbenes photogenerated from the novel bisdiazirine, 1, 3-bis(3-(trifluoromethyl)diazirin-3-yl) benzene 1, have been applied successfully to cross-linking of mono-methyl poly(ethylene oxide) (MePEO5000) in the presence of dichloromethane, leading to the simultaneous incorporation of alkylhalide functionalities. The PEO-based gels swell in a wide range of solvents with polarity index values varying from 3.1 to 9.0. Reaction of the alkylhalide functionalities present in the gels with 4-phenylazophenol provided loading capacities of up to 0.20 mmol g(-1) and demonstrated the potential of these materials for gel-phase synthesis applications. (C) 2008 Elsevier Ltd. All rights reserved.
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In this work we study the colloidal osmotic pressure (COP) and aggregate shape in phosphate saline buffer solutions (PH 7.4) containing bovine serum albumin (BSA), poly(ethylene glycol) lipid (PEG(2000)-PE) and Dextran (Dx). Dx was added to the BSA/PEG(2000)-PE system in order to increase the COP of the solution to levels comparable to the COP of healthy adults, with the aim of using the solution as a blood COP regulator. Dynamic light scattering and small angle X-ray scattering results shown the formation of BSA/PEG(2000)-PE/Dx aggregates in the solution. Osmometry results shown that the addition of Dx to the BSA/PE2000-PE system could successfully increase the COP, through the formation of BSA/PEG(2000)-PE/Dx aggregates. The BSA/PEG(2000)-PE/Dx solutions attained COP= 15 mm Hg, representing 60% of COP measured for healthy adults. (c) 2008 Elsevier B.V. All rights reserved.
