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排序方式: 共有63条查询结果,搜索用时 31 毫秒
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Santini E Guzmán E Ravera F Ferrari M Liggieri L 《Physical chemistry chemical physics : PCCP》2012,14(2):607-615
The properties and structure of different types of interfacial layers obtained from aqueous dispersions of nanometric silica and palmitic acid (PA) have been studied and characterized by different diagnostics and measurements. The investigations concern PA monolayers spread on the silica dispersions, dispersions in contact with PA solutions in oil and silica dispersions containing PA, aiming at elucidating the role of the PA interaction with the particles and investigating the surface-activity of the originated silica-PA complexes. Drop shape tensiometry was utilized to measure the dynamic surface and interfacial tension while a Langmuir trough apparatus was used to obtain compression isotherms of the spread PA layers and to measure the dilational viscoelasticity according to the oscillating barrier method. Brewster angle microscopy and ellipsometry were utilized to investigate the lateral and vertical structure of the interfacial layers. From this multifold approach emerges a complex picture of the features of these interfacial layers that can be rationalized on the basis of the adsorption of PA on the particle surface. The results evidence a threshold in PA adsorption above which particles change from hydrophilic to partially hydrophobic, promoting their incorporation into the interfacial layer. 相似文献
13.
Mariagrazia Bianchi Anna Gillio Berta Mauri Libero Verardi 《Annali di Matematica Pura ed Applicata》1995,169(1):251-268
Subgrouppermutability in a finite group is studied, in order to distinguish between irreducible and reducible groups and to give a bound for the diameter. A simple nonabelian finite group is irreducible and its diameter is less or equal16 while a reducible group is forced to be soluble and the bound of the diameter of such a group is 4.Research partially supported by G.N.S.A.G.A. of C.N.R. and M.U.R.S.T. of Italy. 相似文献
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Compostella F Ronchi S Panza L Mariotti S Mori L De Libero G Ronchetti F 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(21):5587-5595
CD1a protein binds sulfatide (3-O-sulfo-beta-D-galactosylceramide) to form an antigen complex that interacts with T cell receptors and activates T cells. To assess the role of the position of the sulfate in T cell activation, the synthesis of three beta-D-galactosylceramides, variously bearing a sulfate at position 2, 4, or 6 of galactose, has been planned and carried out. The compounds were synthesized by an orthogonal sulfation strategy from a common beta-D-galactosylceramide scaffold, which was in turn obtained through an efficient glycosylation reaction between a fully orthogonally protected galactosyl imidate and 3-O-benzoylazidosphingosine. Immunological evaluation of the three sulfated compounds in CD1a-mediated T cell activation, in comparison with natural sulfatide, provided evidence of the influence of the sulfate position in the recognition event between the antigen, the CD1 protein and the T cell receptor. 相似文献
16.
A novel method, based on the molecular tailoring approach for estimating intramolecular hydrogen bond energies, is proposed. Here, as a case study, the O-H...O bond energy is directly estimated by addition/subtraction of the single point individual fragment energies. This method is tested on polyhydroxy molecules at MP2 and B3LYP levels of theory. It is seen to be able to distinguish between weak ( approximately 1 kcal mol(-1)) and moderately strong ( approximately 5 kcal mol(-1)) hydrogen bonds in polyhydroxy molecules. 相似文献
17.
Kulkarni AD Rai D Bartolotti LJ Pathak RK 《The journal of physical chemistry. A》2006,110(42):11855-11861
The present article comprises a theoretical study of structures and energetics of the lowest energy conformers of peroxyformic acid (PFA) and its hydrated variants, viz. PFA...(H2O)n (n = 1-4), at the molecular level. We have employed two different ab initio quantum chemical methods, viz. restricted Hartree-Fock (RHF) and the second-order M?ller-Plesset (MP2) perturbation theory with the basis sets 6-31G(d,p) and 6-311++G(2d,2p). Modifications in the structure as well as vibrational frequencies of PFA brought about by successive addition of H2O molecules are also discussed. Cooperativity of hydrogen bonding in these clusters can be gauged through a detailed many body interaction energy analysis. 相似文献
18.
Modica E Compostella F Colombo D Franchini L Cavallari M Mori L De Libero G Panza L Ronchetti F 《Organic letters》2006,8(15):3255-3258
[Structure: see text] The C-sulfatide 1b was synthesized through a [2,3]-Wittig sigmatropic rearrangement and a Horner-Wadsworth-Emmons olefination as the key steps. The C-analogue 1b is less immunogenic than natural sulfatide 1a, but induces a preferential secretion of the proinflammatory cytokine IFN-gamma. 相似文献
19.
Hydrogen-bonded heteroclusters of H(2)O(2)...(H(2)O)(n)(), with n varying from 1 through 6, have been investigated herein employing ab initio quantum chemical methods. For a given n, several energetically comparable conformers emerge as local minima on the potential energy surface (PES). All of the conformers obtained at restricted Hartree-Fock (RHF) and M?ller-Plesset second-order perturbation (MP2) levels of theory exhibit parallel trends in energy hierarchy. The effect of clustering by water on the modification in the vibrational frequencies has also been investigated and further, a many-body interaction-energy analysis is carried out providing insights into cooperativity in H(2)O(2)...(H(2)O)(n)() clusters. 相似文献
20.
Density functional theory calculation of gas-phase Delta G of replacement of a water molecule by NH(3) on [M(H(2)O)(6)](n+)(g) for 19 different metal ions correlates well with Delta G of formation of mono NH(3) complexes of these ions in water, suggesting this approach will permit prediction of formation constants in aqueous solution, and produce insights into theories of metal complex formation reactions. 相似文献