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81.
Frédéric Destaillats Cristina Cruz-HernandezKornél Nagy Fabiola Dionisi 《Journal of chromatography. A》2010,1217(9):1543-1548
Monoacylglycerols (MAGs) are lipids found in trace amounts in plants and animal tissues. While they are widely used in various industrial applications, accurate determination of the regio-specific distribution is hindered by the lack of stable, commercially available standards. Indeed, unsaturated β-MAG (or Sn-2 MAG) readily undergoes isomerization into α-MAG (acyl chain is attached to the Sn-1 or the Sn-3 position). In the present study, we describe structural elucidation of α- and β-regio-isomers of monopalmitoyl-glycerol (MAG C16:0) as model compounds in their silylated forms using gas chromatography–mass spectrometry (GC–MS) with electronic impact (EI) ionization. MS fragmentation of α-MAG C16:0 is characterized by the loss of methylene(trimethylsilyl)oxonium (103 amu) and the consecutive loss of acyl chain yielding a fragment ion at m/z 205. The fragmentation pattern of β-MAG C16:0 shows a series of diagnostic fragments at m/z 218, 203, 191 and 103 that are not formed from the α-isomer and hereby enable reliable distinction of these regio-isomers. Possible fragmentation scenarios are postulated to explain the formation of these marker ions, which were also applied to characterize the regio-isomer composition of a complex mixture of MAG sample containing n-3 long-chain polyunsaturated fatty acids. 相似文献
82.
Host–Guest Chemistry: Oxoanion Recognition Based on Combined Charge‐Assisted C−H or Halogen‐Bonding Interactions and Anion⋅⋅⋅Anion Interactions Mediated by Hydrogen Bonds 下载免费PDF全文
Lidia González Dr. Fabiola Zapata Dr. Antonio Caballero Prof. Pedro Molina Prof. Carmen Ramírez de Arellano Prof. Ibon Alkorta Prof. José Elguero 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(22):7533-7544
Several bis‐triazolium‐based receptors have been synthesized and their anion‐recognition capabilities have been studied. The central chiral 1,1′‐bi‐2‐naphthol (BINOL) core features either two aryl or ferrocenyl end‐capped side arms with central halogen‐ or hydrogen‐bonding triazolium receptors. NMR spectroscopic data indicate the simultaneous occurrence of several charge‐assisted aliphatic and heteroaromatic C?H noncovalent interactions and combinations of C?H hydrogen and halogen bonding. The receptors are able to selectively interact with HP2O73?, H2PO4?, and SO42? anions, and the value of the association constant follows the sequence: HP2O73?>SO42?>H2PO4?. The ferrocenyl end‐capped 72+?2 BF4 ? receptor allows recognition and differentiation of H2PO4? and HP2O73? anions by using different channels: H2PO4? is selectively detected through absorption and emission methods and HP2O73? by using electrochemical techniques. Significant structural results are the observation of an anion???anion interaction in the solid state (2:2 complex, 62+? [ H2P2O7 ] 2? ), and a short C?I???O contact is observed in the structure of the complex [ 8 2+][SO4]0.5[BF4]. 相似文献
83.
考察了超临界条件下合成TiO2基光催化剂的性质,尤其是在超临界CO2下得到的分散在TiO2上Pt的特性,并与商品化TiO2性能进行了比较.另外,所得催化剂的光催化活性用CO2光还原制太阳能燃料进行了评价.结果表明,该催化剂可得到具有比商用TiO2更好或类似的性能(高比表面积、结晶度、表面羟基浓度,大的孔容、增强的可见光吸收、高的甲烷生成速率)而用于CO2还原制备燃料的反应中.这可归因于该催化剂超临界介质合成过程. 相似文献
84.
Destaillats F Golay PA Joffre F de Wispelaere M Hug B Giuffrida F Fauconnot L Dionisi F 《Journal of chromatography. A》2007,1145(1-2):222-228
Accurate quantification of trans-fatty acids (TFAs) could be achieved by infrared spectroscopy or by gas-liquid chromatography (GLC). Accurate quantification by GLC should be achieved using specific highly polar capillary columns such as 100 m CP-Sil 88 or equivalent. A pre-fractionation of cis and trans-fatty acids could be performed by silver-ion thin-layer chromatography (Ag-TLC), silver-ion solid-phase extraction (Ag-SPE), or by high-performance liquid-chromatography (HPLC). A pre-fractionation step allows accurate determination of the isomeric profile but it is not essential to achieve quantification of total trans-18:1 isomers nor to determine the level of vaccenic (trans-11 18:1) acid in dairy fat. TFA content could also be calculated in milk fat based on the TAG profile determined by GLC. In this paper, different GLC methods suitable to measure the total of trans-18:1 isomers, vaccenic acid and trans-18:1 acid isomeric distribution in milk fat were compared. Pre-separation of cis- and trans-18:1 isomers by Ag-TLC followed by GLC analysis under optimal conditions was selected as the reference method. Results obtained using alternative methods including pre-separation by HPLC followed by GLC analysis, direct quantification by GLC or calculation from the triacylglycerol (TAG) profile were compared to data acquired using the reference method. Results showed that accurate quantification of total trans-18:1 isomers and vaccenic acid could be achieved by direct quantification by GLC under optimal chromatographic conditions. This method represents a very good alternative to Ag-TLC followed by GLC analysis. On the other hand, we showed that pre-fractionation of fatty acid methyl esters (FAMEs) by HPLC represents a good alternative to Ag-TLC, even if some minor isomers are not selectively purified using this procedure. 相似文献
85.
A normative framework for agent-based systems 总被引:1,自引:0,他引:1
Fabiola López y López Michael Luck Mark d’Inverno 《Computational & Mathematical Organization Theory》2006,12(2-3):227-250
One of the key issues in the computational representation of open societies relates to the introduction of norms that help to cope with the heterogeneity, the autonomy and the diversity of interests among their members. Research regarding
this issue presents two omissions. One is the lack of a canonical model of norms that facilitates their implementation, and
that allows us to describe the processes of reasoning about norms. The other refers to considering, in the model of normative
multi-agent systems, the perspective of individual agents and what they might need to effectively reason about the society
in which they participate. Both are the concerns of this paper, and the main objective is to present a formal normative framework
for agent-based systems that facilitates their implementation.
F. López y López is researcher of the Computer Science Faculty at the Benemérita Universidad Autónoma de Puebla in México, from where she
got her first degree. She also gained a MSc in Computation from the Universidad Nacional Autónoma de México and a PhD in Computer
Science from the University of Southampton in the United Kingdom. She is leading several theoretical and practical projects
that use multi-agent systems as the main paradigm. Her research has been focused on Autonomous Normative Agents and Normative
Multi-Agent Systems and she has published over 20 articles in these and related topics.
M. Luck is Professor of Computer Science in the Intelligence, Agents, Multimedia Group of the School of Electronics and Computer
Science at the University of Southampton, where he carries out research into the theory and practice of agent technology.
He has published over 150 articles in these and related areas, both alone and in collaboration with others, and has published
eight books. He is a member of the Executive Committee of AgentLink III, the European Network of Excellence for Agent-Based
Computing. He is a co-founder of the European Multi-Agent Systems workshop series, is co-founder and Chair of the steering
committee of the UK Multi-Agent Systems Workshops (UKMAS), and was a member of the Management Board of Agentcities.NET. Professor
Luck is also a steering committee member for the Central and Eastern European Conference on Multi-Agent Systems. He is series
editor for Artech House’s Agent Oriented Systems series, and an editorial board member of the Journal of Autonomous Agents
and Multi-Agent Systems, the International Journal of Agent-Oriented Software Engineering, and ACM Transactions on Autonomous
and Adaptive Systems.
M. d’Inverno gained a BA in Mathematics and an MSc in Computation both from Oxford University. He also was awarded a PhD from University
College London. He joined the University of Westminster in 1992 as a Lecturer, became a senior lecturer in 1998, a reader
in 1999 and was appointed professor of computer science in 2001. He is interested in formal, principled approaches to modelling
both natural and artificial systems in a computational setting. The main strand to this research, focuses on the application
of formal methods in providing models of intelligent agent and multi-agent systems. His approach has sought to take a structured
approach to the development of practical agent systems from theoretical models. He has published over 70 articles in these
areas and has published four books and edited collections. 相似文献
86.
J. V. Allaby U. Amaldi G. Barbiellini M. Baubillier F. Bergsma A. Capone W. Flegel F. Grancagnolo L. Lanceri M. Metcalf C. Nieuwenhuis R. Pain J. Panman R. Plunckett K. Winter I. Abt J. Aspiazu A. Bungener F. W. Büsser P. D. Gall T. Hebbeker F. Niebergall P. Schütt P. Stähelin P. Gorbunov E. Grigoriev V. Khovansky A. Rosanov A. Baroncelli L. Barone B. Borgia C. Bosio M. Diemoz C. Dionisi U. Dore F. Ferroni E. Longo P. F. Loverre L. Luminari P. Monacelli S. Morganti F. de Notaristefani C. Santoni L. Tortora V. Valente CHARM Collaboration 《Zeitschrift fur Physik C Particles and Fields》1987,36(4):611-628
The cross-section ratio of neutral-current and charged-current semileptonic interactions of muon-neutrinos on isoscalar nuclei has been measured with the result:R v =0.3093±0.0031 for hadronic energy larger than 4 GeV. From this ratio we determined the electroweak mixing angle sin2 θ W , wherem c is the charm-quark mass in GeV/c2. Comparison with direct measurements ofm w andm z determines the radiative shift of the intermediate boson mass Δr=0.077±0.025(exp.)±0.038(syst.), in agreement with the prediction. Assuming the validity of the electroweak standard theory we determined ?=0.990?0.013(m c ?1.5)±0.009(exp.)±0.003(theor.). 相似文献
87.
C. Bricman C. Dionisi R.J. Hemingway M. Mazzucato L. Montanet N. Barash-Schmidt R.C. Crawford M. Roos A. Barbaro-Galtieri C.P. Horne R.L. Kelly M.J. Losty A. Rittenberg T.G. Trippe G.P. Yost B. Armstrong 《Physics letters. [Part B]》1978,75(1):i-xxi
This review of the properties of leptons, mesons, and baryons is an updating of Review of Particle Properties, Particle Data Group [Rev. Mod. Phys. 48 (1976) No. 2, Part II; and Supplement, Phys. Lett. 68B (1977) 1]. Data are evaluated, listed, averaged, and summarized in tables. Numerous tables, figures, and formulae of interest to particle physicists are also included. A data booklet is available. 相似文献
88.
Enantioselective synthesis of the enantiomer of caloundrin B was achieved by strategic aldol coupling of an enantiopure trioxaadamantane-containing ketone with a racemic pyrone-containing aldehyde via kinetic resolution. In the presence of imidazole, ent-caloundrin B is cleanly isomerized to ent-siphonarin B confirming the proposed structure and absolute configuration for caloundrin B and establishing that it is a plausible biosynthetic product from which siphonarin B and baconipyrones A and C can originate. 相似文献
89.
Direct arylations of pyridine N-oxide (PyO), a convenient method to prepare 2-arylpyridines, catalyzed by Pd(OAc)(2) and PtBu(3) have been proposed to occur by the generation of a PtBu(3)-ligated arylpalladium acetate complex, (PtBu(3))Pd(Ar)(OAc) (1), and the reaction of this complex with PyO. We provide strong evidence that 1 does not react directly with PyO. Instead, our data imply that the cyclometalated complex [Pd(OAc)(tBu(2)PCMe(2)CH(2))](2), which is generated from the decomposition of 1, reacts with PyO and serves as a catalyst for the reaction of PyO with 1. The reaction of PyO with 1 occurs with an induction period, and the reaction of 1 with excess PyO in the presence of [Pd(OAc)(tBu(2)PCMe(2)CH(2))](2) is zeroth-order in 1. Moreover, the rates of reactions of PyO with bromobenzene catalyzed by [Pd(OAc)(tBu(2)PCMe(2)CH(2))](2) and [Pd(PtBu(3))(2)] depend on the concentration of [Pd(OAc)(tBu(2)PCMe(2)CH(2))](2) but not on the concentration of [Pd(PtBu(3))(2)]. Finally, the reaction of 1 with a model heteroarylpalladium complex containing a cyclometalated phosphine, [(PEt(3))Pd(2-benzothienyl)(tBu(2)PCMe(2)CH(2))], rapidly formed the arylated heterocycle. Together, these data imply that the rate-determining C-H bond cleavage occurs between PyO and the cyclometalated [Pd(OAc)(tBu(2)PCMe(2)CH(2))](2) rather than between PyO and 1. In this case, the resulting heteroarylpalladium complex transfers the heteroaryl group to 1, and C-C bond-formation occurs from (PtBu(3))Pd(Ar)(2-pyridyl oxide). This mechanism proposed for the direct arylation of PyO constitutes an example of C-H bond functionalization in which C-H activation occurs at one metal center and the activated moiety undergoes functionalization after transfer to a second metal center. 相似文献
90.
Priefer R Lee YJ Barrios F Wosnick JH Lebuis AM Farrell PG Harpp DN Sun A Wu S Snyder JP 《Journal of the American Chemical Society》2002,124(20):5626-5627
Dicubyl disulfide (1) has been prepared in six steps from commercially available dimethyl-1,4-cubanedicarboxylate in 47% overall yield. In the final step, the previously unknown cubanethiol 2 was oxidized to disulfide 1. X-ray crystallography for 1 reveals the shortest tetragonal C-S bond on record (1.771 A). In contrast to previous generalizations, density functional theory calculations predict a low S-S rotation barrier similar to that for t-BuSSBu-t. Low-temperature (13)C NMR (600 MHz) confirms the prediction. 相似文献