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281.
Thi Thanh Thuy N'Guyen Karima Oussadi Véronique Montembault Laurent Fontaine 《Journal of polymer science. Part A, Polymer chemistry》2013,51(2):415-423
The synthesis of new ω‐phosphonic acid‐terminated poly(ethylene oxide) (PEOs) monomethyl ethers was investigated by the combination of Atherton–Todd or Kabachnik–Fields reactions and the “click” copper‐catalyzed 1,3‐dipolar cycloaddition of azides and terminal alkynes. The Atherton–Todd route fails to give the corresponding phosphonic acid‐terminated PEOs due to competitive cleavage of the P? N bond during the dealkylation step. In contrast, the Kabachnik–Fields route leads with very good yields to ω‐phosphonic acid‐PEO through “click” reaction of azido‐PEO onto dimethyl aminopropargyl phosphonate prepared by Kabachnik–Fields reaction between propargylbenzylimine and dimethyl phosphonate, followed by acidic hydrolysis. The reported methodology, precluding the use of anionic polymerization of ethylene oxide, leads to novel well‐defined phosphonic acid‐terminated PEOs from commercially available products in good yields. Moreover, such a strategy can be adapted to anchor phosphonic acid functionality onto a wide range of polymers. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013 相似文献
282.
Redouan Elboutachfaiti Roland Molini David Mathiron Yannis Maillot Jean-Xavier Fontaine Serge Pilard Anthony Quro Clment Brasselet Marguerite Dols-Lafargue Cdric Delattre Emmanuel Petit 《Molecules (Basel, Switzerland)》2022,27(7)
In vitro culture of flax (Linum usitatissimum L.) was exposed to chitosan oligosaccharides (COS) in order to investigate the effects on the growth and secondary metabolites content in roots and shoots. COS are fragments of chitosan released from the fungal cell wall during plant–pathogen interactions. They can be perceived by the plant as pathogen-associated signals, mediating local and systemic innate immune responses. In the present study, we report a novel COS oligosaccharide fraction with a degree of polymerization (DP) range of 2–10, which was produced from fungal chitosan by a thermal degradation method and purified by an alcohol-precipitation process. COS was dissolved in hydroponic medium at two different concentrations (250 and 500 mg/L) and applied to the roots of growing flax seedlings. Our observations indicated that the growth of roots and shoots decreased markedly in COS-treated flax seedlings compared to the control. In addition, the results of a metabolomics analysis showed that COS treatment induced the accumulation of (neo)lignans locally at roots, flavones luteolin C-glycosides, and chlorogenic acid in systemic responses in the shoots of flax seedlings. These phenolic compounds have been previously reported to exhibit a strong antioxidant and antimicrobial activities. COS oligosaccharides, under the conditions applied in this study (high dose treatment with a much longer exposure time), can be used to indirectly trigger metabolic response modifications in planta, especially secondary metabolism, because during fungal pathogen attack, COS oligosaccharides are among the signals exchanged between the pathogen and host plant. 相似文献
283.
A. A. Fontaine S. Deutsch T. A. Brungart H. L. Petrie M. Fenstermacker 《Experiments in fluids》1999,26(5):397-403
The influence of homogeneous surfactant and homogeneous polymer solutions on the performance of microbubble skin friction
reduction was investigated on an axisymmetric body. Carbon dioxide was injected into water, homogeneous surfactant (Aerosol
OT) solutions, and homogeneous dilute polymer (Polyethylene oxide) solutions. Integrated skin friction measurements were obtained
at two freestream velocities as a function of gas injection rate and polyethylene-oxide concentration. A moderate (50%) decrease
in surface tension had little to no effect on the drag reducing characteristics of microbubble injection. At similar gas injection
rates, microbubble injection exhibited more drag reduction in the polymer solutions than obtained with microbubble injection
into water. However, the increased drag reduction obtained with polymer additives was no more than a multiplicative factor
related to the baseline levels of drag reduction achieved by the individual methods, and suggests the mechanism for microbubble
skin friction reduction acts independently of the polymer drag reduction.
Received: 17 April 1998 / Accepted: 12 October 1998 相似文献
284.
M. Münzenberg M. Arend W. Felsch S. Pizzini A. Fontaine T. Neisius S. Pascarelli 《Journal of magnetism and magnetic materials》2000,220(2-3)
Fe/Ce multilayers are magnetically soft with coercive fields of a few Oersteds. In this artificial system, the itinerant 5d electrons of Ce are magnetically polarized by hybridization with the spin–split 3d states of Fe. To obtain an insight into the magnetization reversal process, the element selectivity of X-ray magnetic circular dichroism was used to measure the magnetization of the Ce-5d electrons as a function of an applied magnetic field. Comparison with the magnetization curves studied by the magneto-optic Kerr effect, which averages over the whole system, revealed that the coercivity in the hysteresis of the ordered Ce-5d moments is reduced by 50%. We propose that this is an effect of the magnetically disturbed interface or of the complex non-collinear magnetic structure of the Ce layers detected by recent experiments of X-ray resonant magnetic scattering. The results are compared to the X-ray dichroic and Kerr hysteresis loops of the multilayers Fe/La/Ce/La and Fe/CeH2−δ. These systems are magnetically harder and their coercivities are identical. 相似文献
285.
Electrochemical Monitoring of the Early Events of Hydrogen Peroxide Production by Mitochondria
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Dr. Emmanuel Suraniti Salem Ben‐Amor Pauline Landry Prof. Michel Rigoulet Prof. Eric Fontaine Prof. Serge Bottari Dr. Anne Devin Prof. Neso Sojic Dr. Nicolas Mano Dr. Stéphane Arbault 《Angewandte Chemie (International ed. in English)》2014,53(26):6655-6658
Mitochondria consume oxygen in the respiratory chain and convert redox energy into ATP. As a side process, they produce reactive oxygen species (ROS), whose physiological activities are still not understood. However, current analytical methods cannot be used to monitor mitochondrial ROS quantitatively and unambiguously. We have developed electrochemical biosensors based on peroxidase‐redox polymer‐modified electrodes, providing selective detection of H2O2 with nanomolar sensitivity, linear response over five concentration decades, and fast response time. The release of H2O2 by mitochondria was then monitored under phosphorylating or inhibited respiration conditions. We report the detection of two concomitant regimes of H2O2 release: large fluxes (hundreds of nM ) under complex III inhibition, and bursts of a few nM immediately following mitochondria activation. These unprecedented bursts of H2O2 are assigned to the role of mitochondria as the hub of redox signaling in cells. 相似文献
286.
J. R. Fontaine 《Journal of statistical physics》1981,26(4):767-782
We consider a classical dipole gas in the grand canonical ensemble. We prove that in dimensions greater than or equal to three, and for all temperatures, the free energy and the charges-dipoles correlation functions have an expansion in powers ofz, the fugacity of the system, which is asymptotic to all orders. We also give some information about the decay of correlations.on leave from Institut de Physique Théorique Université de Louvian, Belgium. Supported by N.S.F. grant No. PHY-15920. 相似文献
287.
D. Drijard H.G. Fischer R. Gokieli P.G. Innocenti V. Korbel A. Minten A. Norton R. Sosnowski S. Stein H.D. Wahl M. Della Negra G. Fontaine P. Frenkiel C. Ghesquiere D. Linglin G. Sajot H. Frehse D. Wegener 《Nuclear Physics B》1978,143(1):61-80
Using the split field magnet (SFM) of the CERN ISR, we have investigated the main features of the reaction pp → ppπ+π? in the kinematical region where double pomeron exchange (DPE) is supposed to play an important rôle. Using kinematically fitted events at the five standard ISR energies from √s = 23.4 GeV to √s = 63.4 GeV, we have studied different data subsamples as a means of distinguishing DPE from the tail of single diffraction (SD). Our results are compatible with a significant DPE contribution; in particular there is no correlation between the two protons and the s- and t-dependences follow the expected behaviour. 相似文献
288.
We present a new method for measuring the anisotropy of the orientational probability function of CN- ions in a f.c.c. NaCN crystal. The results are discussed and compared with previous neutron diffraction measurements. 相似文献
289.
Dr. Thuy T. T. N'Guyen Hien T. T. Duong Johan Basuki Dr. Véronique Montembault Dr. Sagrario Pascual Clément Guibert Dr. Jérôme Fresnais Assoc. Prof. Dr. Cyrille Boyer Dr. Michael R. Whittaker Prof. Dr. Thomas P. Davis Prof. Dr. Laurent Fontaine 《Angewandte Chemie (International ed. in English)》2013,52(52):14152-14156
290.
O. Uteza P. Delaporte B. Fontaine B. Forestier M. Sentis I. Tassy J.P. Truong 《Applied physics. B, Lasers and optics》1998,66(1):31-37
Received: 3 January 1997/Revised version: 13 May 1997 相似文献