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1.
Thierry Woignier G. Pochet H. Doumenc P. Dieudonné L. Duffours 《Journal of Sol-Gel Science and Technology》2007,41(1):25-30
Volcanic (allophanic) soils are interesting in terms of the control of the greenhouse effect and the knowledge of the porous
features is of importance to understand the mechanism of C and N sequestration. These soils contain a peculiar clay: allophane
aggregates quite close to the synthetic mineral gels aggregates. These volcanic materials behave as gels during drying with
a large irreversible shrinkage that can modify the soil physical properties. Consequently, as for silica gels, we use the
CO2 supercritical drying procedure (SD) to control the drying step and to preserve the structural and textural properties of
the soils. The experimental results show that the N and C content in the soils is clearly dependent on the allophane content.
We also show that the textural properties, such as specific surface area, are higher for the supercritically dried samples,
compared to the classically dried samples, and SAXS results confirm the preserving effect of the SD. With these data, we propose
possible effects of the specific surface area on the C and N content of the allophanic soils. 相似文献
2.
Job Tchoumtchoua Dieudonné Njamen Jean Claude Mbanya Alexios‐Leandros Skaltsounis Maria Halabalaki 《Journal of mass spectrometry : JMS》2013,48(5):561-575
Hyphenated techniques and especially ultra‐high performance liquid chromatography‐mass spectrometry (UHPLC‐MS) are nowadays widely employed in natural products research. However, the complex nature of plant extracts complicates considerably the analysis and the identification of their constituents. Nevertheless, new MS analyzers with increased resolving power and accuracy such as the orbital trap (Orbitrap) could facilitate drastically this process. The objective of this study is the development of a new structure‐oriented approach based on fast UHPLC‐high‐resolution (HR)MS and HRMS/MS methodologies for the identification of isoflavonoids in crude extracts. In addition, aims to assist dereplication procedures, to decrease the laborious isolation steps and orient the focused isolation of compounds of interest. As a proof of concept, the methanol extract of the stem bark of Amphimas pterocarpoides (Leguminosae) was selected. Based on chromatographic (retention time, polarity) and spectrometric features (ultraviolet spectra, accurate m/z, proposed elemental composition, ring double bond equivalent, and relative isotopic abundance) as well as HRMS/MS spectra, several isoflavonoids were identified. In order to verify the proposed structures, 11 isoflavonoids were selectively isolated and unambiguously identified using 1&2D nuclear magnetic resonance techniques. Moreover, the isolated isoflavonoids were studied in HRMS/MS level, employing electrospray ionization and atmospheric pressure chemical ionization sources, in both modes. Useful information regarding their fragmentation patterns was obtained, and characteristic diagnostic ions were defined for the identification of methoxylated isoflavones, dihydroisoflavones and 5‐hydroxylated isoflavonoids. Based on the current results, the proposed dereplication strategy was verified and could comprise a novel approach for the analysis of crude extracts in the future not only for isoflavonoids but also for other chemical classes of natural products. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
3.
Mohamed Fatnassi Corine Tourné-Péteilh Pradial Peralta Thomas Cacciaguerra Philippe Dieudonné Jean-Marie Devoisselle Bruno Alonso 《Journal of Sol-Gel Science and Technology》2013,68(2):307-316
Two model drugs of different physico-chemical and pharmaceutical properties (ibuprofen, acetaminophen) have been incorporated together or separately in silica-based microspheres using sol–gel and spray-drying processes. A variable amount of a neutral surfactant Brij-56© has also been added. The properties of the microspheres vary significantly depending on their composition. Three kinds of texture are identified: (1) silica containing spheroid nano-domains (formed by ibuprofen; diameters between 20 and 100 nm), (2) silica containing worm-like mesophases (formed by Brij-56© and both model drugs, typical correlation distances ~6 nm), (3) silica intimately mixed with the drug (acetaminophen) without visible phase-separation. The kinetics of drug release in simulated intestinal fluid strongly depend on these textures. The association of ibuprofen and acetaminophen in a single type of microsphere and without surfactant favours a concomitant release. Possible mechanisms of materials’ formation are discussed. 相似文献
4.
Jean Dieudonné 《Mathematische Annalen》1966,163(1):1-3
Sans résuméA MoniseurG. Köthe, à l'occasion de son soixantième anniversaire 相似文献
5.
6.
Fehr C Dieudonné P Primera J Woignier T Sauvajol JL Anglaret E 《The European physical journal. E, Soft matter》2003,12(Z1):S13-S16
Solid polymorphism of 4-alkyl-4'-cyanobiphenyl (nCB) was studied so far as a function of thermal history. In this paper we show that metastable solid phases of 4-octyl-4'-cyanobiphenyl (8CB) are also formed when the mesogens are confined in porous silica matrices and we study their structure by neutron diffraction and by Raman spectroscopy. Three metastable solid states are identified: one crystalline phase K', two frozen-in smectic-like phases K(s) and K'(s). We discuss the relation between the structure of the metastable solid phases and that of the mesomorph phases. 相似文献
7.
This paper resolves a recent conjecture of I. Kaplansky concerning the nonsingularity of linear maps that preserve the set of nonzero specializations of polynomials. 相似文献
8.
Olivier Placide Noté Anne‐Claire Mitaine‐Offer Tomofumi Miyamoto Thomas Paululat Dieudonné Emmanuel Pegnyemb Marie‐Aleth Lacaille‐Dubois 《Magnetic resonance in chemistry : MRC》2009,47(3):277-282
From the stem bark of Tetrapleura tetraptera, two new oleanane‐type saponins, tetrapteroside A 3‐O‐{6‐O‐[(2E,6S)‐2,6‐dimethyl‐6‐hydroxyocta‐2,7‐dienoyl]‐β‐D ‐glucopyranosyl‐(1 → 2)‐β‐D ‐glucopyranosyl‐(1 → 3)‐β‐D ‐glucopyranosyl‐(1 → 4)‐[β‐D ‐glucopyranosyl‐(1 → 2)]‐β‐D ‐glucopyranosyl}‐3,27‐dihydroxyoleanolic acid (1), and tetrapteroside B 3‐O‐{ β‐D ‐glucopyranosyl‐(1 → 2)‐6‐O‐[(E)‐feruloyl]‐β‐D ‐glucopyranosyl‐(1 → 3)‐β‐D ‐glucopyranosyl‐(1 → 4)‐[β‐D ‐glucopyranosyl‐(1 → 2)]‐β‐D ‐glucopyranosyl}‐3,27‐dihydroxyoleanolic acid (2), were isolated. Further extractions from the roots led to the isolation of four known oleanane‐type saponins. Their structures were elucidated by the combination of mass spectrometry (MS), one and two‐dimensional NMR experiments. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
9.
Olivier Placide Noté Philippe Chabert Dieudonné Emmanuel Pegnyemb Bernard Weniger Marie‐Aleth Lacaille‐Dubois Annelise Lobstein 《Magnetic resonance in chemistry : MRC》2010,48(10):829-836
Three new acacic acid derivatives, named coriariosides C, D, and E ( 1–3 ) were isolated from the roots of Albizia coriaria. Their structures were elucidated on the basis of extensive 1D‐ and 2D‐NMR studies and mass spectrometry as 3‐O‐[β‐D ‐xylopyranosyl‐(1 → 2)‐β‐D ‐fucopyranosyl‐(1 → 6)‐2‐(acetamido)‐2‐deoxy‐β‐D ‐glucopyranosyl]‐21‐O‐{(2E,6S)‐6‐O‐{4‐O‐[(2E,6S)‐2,6‐dimethyl‐ 6‐O‐(β‐D ‐quinovopyranosyl)octa‐2,7‐dienoyl]‐4‐O‐[(2E,6S)‐2,6‐dimethyl‐6‐O‐(β‐D ‐quinovopyranosyl)octa‐2,7‐dienoyl]‐β‐D ‐quinovopyranosyl}‐2,6‐dimethylocta‐2,7‐dienoyl}acacic acid 28‐O‐β‐D ‐xylopyranosyl‐(1 → 4)‐α‐L ‐rhamnopyranosyl‐(1 → 2)‐β‐D ‐glucopyranosyl ester ( 1 ), 3‐O‐{β‐D ‐fucopyranosyl‐(1 → 6)‐[β‐D ‐glucopyranosyl‐(1 → 2)]‐β‐D ‐glucopyranosyl}‐21‐O‐{(2E,6S)‐6‐O‐{4‐O‐[(2E,6S)‐2,6‐dimethyl‐6‐O‐(β‐D ‐quinovopyranosyl)octa‐2,7‐dienoyl]‐4‐O‐[(2E,6S)‐2,6‐dimethyl‐6‐O‐(β‐D ‐quinovopyranosyl)octa‐2,7‐dienoyl]‐β‐D ‐quinovopyranosyl}‐2,6‐dimethylocta‐2,7‐dienoyl}acacic acid 28‐O‐α‐L ‐rhamno pyranosyl‐(1 → 2)‐β‐D ‐glucopyranosyl ester ( 2 ), and 3‐O‐[β‐D ‐fucopyranosyl‐(1 → 6)‐β‐D ‐glucopyranosyl]‐21‐O‐{(2E,6S)‐6‐O‐{4‐O‐[(2E,6S)‐2,6‐dimethyl‐6‐O‐(β‐D ‐quinovopyranosyl)octa‐2,7‐dienoyl)‐β‐D ‐quinovopyranosyl]octa‐2,7‐dienoyl}acacic acid 28‐O‐β‐D ‐glucopyranosyl ester ( 3 ). Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
10.