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81.
Michel Gratton Camille Gontier Saïd Rja Fi Allah Abdelhake Bouchou Didier Picart 《European Journal of Mechanics - A/Solids》2009,28(5):935-947
The present paper deals with the characterisation of the static mechanical behaviour of an energetic material all along its lifespan. The material behaviour is viscoplastic, damageable and sensitive to hydrostatic pressure. For such materials, existing models have generally been developed in the framework of transient dynamic behaviour. These models are not suitable for a static study. Therefore a specific experimental protocol and an associated model are developed. Characterisation is derived from both uniaxial compressive, tensile tests and triaxial tests. Plastic behaviour is described by means of a parabolic yield criterion and a new hardening law. Non-associated plastic flow rule and isotropic damage complete the model. The performance of the model is illustrated through the simulation of various loading paths. 相似文献
82.
Collet F Lescot C Liang C Dauban P 《Dalton transactions (Cambridge, England : 2003)》2010,39(43):10401-10413
Stereoselective catalytic intermolecular C-H amination of complex molecules is reported. Site-selective functionalizations occur with very good yields up to 91% and excellent d.e.s up to 99%. However, the precise nature of the nitrene C-H insertion remains a matter of debate despite several physical organic experiments. 相似文献
83.
Matrab T Yassar A Viau G Chakroune N Fievet F Lacaze PC 《Journal of colloid and interface science》2006,296(1):95-101
Monodisperse ruthenium nanoparticles functionalized by electroactive oligothiophenes have been prepared and characterized. Using TEM, UV-visible and FTIR we established that the organization of these nanoparticles into nanospheres can be directly controlled via modulation of the pi-pi interaction between the organic components adsorbed on the surface. This finding also shows that the self-assembled nanoheterostructures may be switched from monodisperse nanoparticles to ordered nanospheres by tuning the pH. 相似文献
84.
85.
D. Goulder T. Blaffert A. Blokland L. Buydens A. Chhabra A. Cleland N. Dunand H. Hindriks G. Kateman H. van Leeuwen D. Massart A. Mulholland G. Musch P. Naish A. Peeters G. Postma P. Schoenmakers M. de Smet B. Vandeginste J. Vink 《Chromatographia》1988,26(1):237-243
Summary This paper gives an overview of the structure and processes going on in the project Expert Systems for Chemical Analysis (ESCA), an international project within the ESPRIT research programme of the European Community. The application area, HPLC method development, is explained and broken down into four domains. The methods used for representing knowledge in the project are discussed. 相似文献
86.
Bernhard Schnenberger Walter Summermatter Camille Ganter 《Helvetica chimica acta》1982,65(7):2333-2337
An enantioselective synthesis of key intermediates for the synthesis of the anti-microbially active pseudomonic acids A ( 1 ), B ( 2 ) and C ( 3 ) is described. D -Ribose ( 4 ) was used as starting material. 相似文献
87.
Duygu Avci Camille Haynes Lon J. Mathias 《Journal of polymer science. Part A, Polymer chemistry》1997,35(10):2111-2121
New diacrylate monomers for cyclopolymerization were synthesized from the reaction of ethyl α-chloromethylacrylate (ECMA) and t-butyl α-bromomethyl acrylate (TBBr) with aniline, adamantyl amine, t-butyl amine, cyanamide, and 4-tetradecyl aniline in yields of ca. 50–70%. Bulk and solution polymerizations with azobisisobutyronitrile (AIBN) at 60–85°C gave soluble cyclopolymers with Mn and Mw ranging from 10,000–30,000 and 12,000–40,000, respectively. The ECMA–cyanamide derivative only gave crosslinked polymers. 1H and 13C solution NMR indicated high cyclization efficiency (>93%). A prototype NLO polymer was synthesized from the reaction of the TBBr–aniline cyclopolymer with tetracyanoethylene. The p-hydroxyaniline derivative of ECMA was synthesized and used for further derivatizations; for example, the benzoate ester was made and polymerized (Mn = 21,260 and Mw = 40,317). The ester groups of the TBBrndash;aniline polymer were hydrolyzed completely to give a polymer with both acid and base moieties. DSC thermograms showed glass transitions of 132°C for the ECMA–aniline derivative, 192°C for the ECMA–adamantyl derivative, 53°C for the TBBr–tetradecylaniline derivative, and 120° for the ECMA–p-benzoylaniline derivative. The ECMA–t-butyl amine polymer showed no obvious Tg. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2111–2121, 1997 相似文献
88.
A mechanistic model is presented for the base‐catalyzed intramolecular cyclization of polycyclic unsaturated alcohols of type A to ethers D (Scheme 1). The alkoxide anion B is formed first in a fast acid‐base equilibrium. For the subsequent reaction to D , a carbanion‐like transition state C is proposed. This mechanism is in full agreement with our results regarding the influence of substituents on the regioselectivity and the rate of cyclization. We studied the effect of alkyl substituents in allylic position (alkylated endocylic olefinic alcohols 1 – 3 ) and, especially, at the exocyclic double bond ( 12 – 15 ). The fastest cyclization (krel=1) is 12 → 16 , which proceeds via a primary carbanion‐like transition state ( E : R1=R2=H). The corresponding processes 13 → 17 and 14 → 17 are characterized by a less‐stable secondary carbanion‐like transtition state ( E : R1=Me, R2=H, or vice versa) and are slower by a factor of 104. The slowest reaction (krel ca. 10−6) is the cyclization 15 → 18 via a tertiary carbanion‐like transition state ( E : R1=R2=Me). 相似文献
89.
Marion Devaux Jaleh Ghashghaie Didier Bert Catherine Lambrot Arthur Gessler Camille Bathellier Jérôme Ogee Denis Loustau 《Rapid communications in mass spectrometry : RCM》2009,23(16):2511-2518
The study presents a comparison of two phloem sugar extraction methods. The amount of phloem sugar extracted and the carbon isotope composition (δ13C) of the total extracts and of the main phloem compounds separated by high‐performance liquid chromatography (sucrose, glucose, fructose and pinitol) are compared. These two phloem sap extraction methods are exudation in distilled water and a new method using centrifugation, which avoids the addition of any solvent. We applied both extraction methods on phloem discs sampled from 38‐year‐old Pinus pinaster trees in south‐western France throughout the period from June 2007 to December 2008 on different time‐scales: hourly, daily and monthly. We found that the centrifugation method systematically extracted ca. 50% less compounds from the phloem discs than the exudation method. In addition, the two extraction methods provided similar δ13C values of the total extracts, but the values obtained by the exudation method were 0.6‰ more negative than those calculated from the mass balance using the individual constituents. Over the growing season, both extraction methods exhibited lower total sugar content and more 13C‐enriched phloem sap in summer compared with winter values. These findings suggest that both extraction methods can be applied to study the carbon isotope composition of phloem sap, and the centrifugation method has the advantage that no solvent has to be added. The exudation method, however, is more appropriate for the quantification of the amounts of phloem sugars. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
90.
Jeremy E. Melanson Brian L. -Y. Wong Camille A. Boulet Charles A. Lucy 《Journal of chromatography. A》2001,920(1-2):359-365
Capillary electrophoresis coupled with indirect UV absorbance detection was employed for the determination of the chemical warfare agent degradation products: methylphosphonic acid, ethyl methylphosphonate, isopropyl methylphosphonate, and pinacolyl methylphosphonate. Glutamic acid was used as a buffering agent at its isoelectric point (pH 3.22). In its zwitterionic form, glutamic acid does not act as a competing co-anion in the system, thus providing buffering capacity while maintaining high sensitivity. The indirect probe (phenylphosphonic acid) concentration was lowered to 1 mM from the 10 mM in previous literature studies, further enhancing sensitivity. Detection limits of 2 μM were achieved with hydrodynamic injection and up to 100-fold lower using electrokinetic injection. The increased buffering capacity of this system over previous methods led to migration time reproducibility RSD values of 0.18 to 0.22%. This represents a 10-fold improvement in reproducibility over previous studies with comparable or improved sensitivity. 相似文献