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471.
Gianni P Barghini A Bernazzani L Mollica V 《Langmuir : the ACS journal of surfaces and colloids》2006,22(19):8001-8009
The interaction of lithium perfluorononanoate (LiPFN) with poly(ethylene glycol) (PEG) molecules of different molecular weights (300 < MW < 20000 Da) has been investigated in water at 298.15 and 308.15 K by isothermal titration calorimetry (ITC). Density, viscosity, and conductivity measurements were also performed at 298.15 K. The aggregation process of this surfactant on the PEG polymeric chain was found to be very similar to that exhibited by cesium perfluorooctanoate (CsPFO) and appears to be consistent with the necklace model. ITC titrations indicated that a fully formed LiPFN micellar cluster can be wrapped by a PEG chain having a molecular weight (MW) of approximately 3200 Da, longer than that required by the shorter perfluorooctanoate (MW approximately 2600 Da), and also suggested a stepwise mechanism for the aggregation of successive micelles. Viscosity data indicate that the formation of polymer-surfactant complexes between PEG and LiPFN involves a conformational change of the polymer. The aggregation of preformed micelles of LiPFN or CsPFO or SDS on the PEG polymeric chain always gives rise to further stabilization. 相似文献
472.
Faralli C Pagliai M Cardini G Schettino V 《The journal of physical chemistry. B》2006,110(30):14923-14928
A Car-Parrinello molecular dynamics simulation has been performed on a solution of Br- in liquid methanol analyzing with particular attention charge transfer and polarization effects. The first solvation shell has been characterized in terms of H-bonds, and it has been found that the high polarization of the bromide gives rise to a stable solvent cage. The differences in the coordination number with the chloride can be ascribed to the ionic radius and to the stronger perturbations brought by the solvent to the bromide ion. 相似文献
473.
Begala M Tocco G Delogu G Meli G Picciau C Podda G 《Journal of mass spectrometry : JMS》2006,41(5):577-585
The mass spectrometric behaviour of a series of 6,6-disubstituted dibenzo(d,f)(1,3)dioxepine derivatives have been studied. The fragmentation patterns were described and discussed in detail with the aid of labelled compounds, accurate mass measurements and collisionally induced dissociation experiments performed using an ion trap. 相似文献
474.
Guizzunti G Brady TP Malhotra V Theodorakis EA 《Journal of the American Chemical Society》2006,128(13):4190-4191
The chemical origin of the norrisolide-induced irreversible Golgi vesiculation was studied using a variety of norrisolide probes. This natural product was found to bind to a receptor on the Golgi membranes using the perhydroindane core fragment as the recognition element. The acetylated gamma-lactol-gamma-lactone side chain of norrisolide is essential for the irreversible Golgi vesiculation and can be replaced by other electrophilic motifs without loss of biological function. In particular, compound 10 reproduces the cellular phenotype of the natural product. 相似文献
475.
C Falavigna M Cirlini G Galaverna S Sforza A Dossena C Dall'asta 《Journal of mass spectrometry : JMS》2012,47(9):1170-1176
Fumonisins are a family of food-borne mycotoxins with a wide spectrum of toxicological activities, produced by Fusarium verticillioides. Twenty-eight fumonisin analogues have been characterised so far, which can be separated into four main groups, identified as fumonisin A, B, C and P, being fumonisin B the most widely occurring in maize and corn-based food. In this work, major and minor fumonisin analogues produced by F. verticillioides have been determined by the development of a suitable tandem mass spectrometry procedure for target compound identification and quantification. The method has been applied to the determination of the major fumonisins in culture media of F. verticillioides and in mouldy maize. In addition to the main fumonisins produced by F. verticillioides, also secondary compounds such as FB4, FB5, FAs and FCs have been detected in both fungal liquid cultures and contaminated maize samples. The use of this method for quantification of major and minor fumonisins may be useful for an exhaustive evaluation of their occurrence and toxicological relevance in food; moreover, it may be applied for a better definition of the fumonisin biosynthetic pathways in different growing media as well as in maize. Copyright ? 2012 John Wiley & Sons, Ltd. 相似文献
476.
Antonio Arcelli Alessandro Bongini Gianni Porzi Samuele Rinaldi 《Journal of Physical Organic Chemistry》2012,25(2):132-141
The ammonolysis of three morpholine‐2,5‐dione derivatives was investigated and the mechanism ascertained by kinetic studies and theoretical calculations. The kinetics, followed by high‐performance liquid chromatography analysis, evidenced the presence of two intermediates, which were isolated and characterized. The ammonolysis occurs with a complex mechanism involving two consecutive reactions followed by two parallel ones. The second step of the whole reaction involves an anchimeric assistance of the primary amide group. The pseudo‐first‐order rate constants were calculated by appropriate equations, which describe the single steps of the process. Computational density functional theory investigations of vicinal primary amide group participation were performed using a model compound, and the transition states were generated. The theoretical calculations evidenced the essential role exerted by ammonia, which acts as a proton transfer. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
477.
Elena Botta Tullio Bressani Gianni Garbarino 《The European Physical Journal A - Hadrons and Nuclei》2012,48(3):1-64
Selected topics in strangeness nuclear physics are critically reviewed. This includes production, structure and weak decay of ??-Hypernuclei, the $\bar K$ nuclear interaction and the possible existence of $\bar K$ bound states in nuclei. Perspectives for future studies on these issues are also outlined. 相似文献
478.
D.E. Lucchetta R. Castagna F. Vita A. Gianni F. Simoni 《Photonics and Nanostructures》2012,10(4):575-580
We recently developed a novel composite photopolymerizable material which allows the holographic recording of diffraction gratings with optimal optical and mechanical properties (high diffraction efficiency, transparency and spatial resolution, low shrinkage, long time stability). This material was successfully used to produce a low cost and easy to make optically pumped, organic distributed feedback laser, working on the first diffraction order of a high quality Bragg grating doped with a photoluminescent dye. Here we show the possibility of positioning these micrometer sized light sources at any point of a generic lab-on-a-chip device by borrowing experimental techniques commonly used in the fields of microfluidics and optofluidics. In particular, a microfluidic channel has been imprinted by soft lithography in a polydimethylsiloxane substrate in order to convey the photopolymerizable mixture to a particular area of the sample, where the laser device has been holographically recorded. A characterization of the lasing properties of this device has been carried out. The proposed approach allows a better confinement of the emitted light and overcomes some physical constrains (resolution, aspect ratio) of PDMS based microfluidic laser thus opening new possibilities for the complex integration of organic laser sources in lab-on-a-chip devices. 相似文献
479.
Paolo Aniello Gianni Cassinelli Ernesto De Vito Alberto Levrero 《Journal of Fourier Analysis and Applications》2001,7(2):199-206
For groups which are the semidirect product of some vector group with a unimodular group we prove that the existence of a
discrete frame obtained from an at-most countable set of vectors through the action of a given unitary representation implies
that the representation in use has to be square-integrable. 相似文献
480.
M. Sangermano E. Amerio A. Di Gianni A. Priola D. Pospiech B. Voit 《Macromolecular Symposia》2007,254(1):9-15
Summary: A wide range of hyperbranched polymers (HBP) was synthesized and investigated as additives in cationic photopolymerization of epoxy systems. The HBP were inserted into the polymeric network either by a copolymerization or through a chain transfer reaction involving the phenolic hydroxyl groups. By varying the type and concentration of HBP a modification of the bulk properties of photocured films was induced. An increase of toughness properties together with a flexibilization was obtained without affecting the processability and the viscosity of the photocurable mixture. In the presence of fluorine-containing HBP, a surface modification was induced. 相似文献