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141.
Burriel P Ignés-Mullol J Reigada R Sagués F 《Langmuir : the ACS journal of surfaces and colloids》2006,22(1):187-193
Langmuir monolayers of an amphiphilic azobenzene derivative exhibit easily perturbable mesophases with long-range orientational order that couples strongly to linearly polarized light, resulting in symmetric photoaligned textures. Controlled rotation of the polarization plane induces continuous collective precession of the molecular field, which reveals the shear-thinning nature of the surface rotational viscosity. The dynamics is controlled by a balance between the strength of the optical coupling and viscous dissipation so that an increase in the rotational velocity results in a dampening of the synchronous anharmonic oscillations of the orientational field, as revealed by a space-time analysis of the Brewster angle microscopy images. 相似文献
142.
A regioselective 6-endo reductive cyclization of 2-indolylacyl radicals constitutes the key step of a straightforward synthetic entry to the olivacine skeleton, illustrated by a total synthesis of the tetrahydropyridine alkaloid guatambuine. 相似文献
143.
Praveen Kumar Antoni Rúbies Ramon Companyó Francesc Centrich 《Journal of separation science》2012,35(20):2710-2717
Two methods based on liquid chromatography–tandem mass spectrometry were developed for the determination of ten aminoglycosides (streptomycin, dihydrostreptomycin, spectinomycin, apramycin, paromomycin, kanamycin A, gentamycin C1, gentamycin C2/C2a, gentamycin C1a, and neomycin B) in kidney samples from food‐producing animals and in honey samples. The methods involved extraction with an aqueous solution (for the kidney samples) or sample dissolution in water (for the honey samples), solid‐phase extraction with a weak cation exchange cartridge and injection of the eluate into a liquid chromatography–tandem mass spectrometry system. A zwitterionic hydrophilic interaction chromatography column was used for separation of aminoglycosides and a triple quadrupole mass analyzer was used for detection. The methods were validated according to Decision 2002/657/EC. The limits of quantitation ranged from 2 to 125 μg/kg in honey and 25 to 264 μg/kg in the kidney samples. Interday precision (RSD%) ranged from 6 to 26% in honey and 2 to 21% in kidney. Trueness, expressed as the percentage of error, ranged from 7 to 20% in honey and 1 to 11% in kidney. 相似文献
144.
Ramon S. Vilela Thiago L. Oliveira Felipe T. Martins Javier A. Ellena Francesc Lloret Miguel Julve Danielle Cangussu 《Comptes Rendus Chimie》2012,15(10):856-865
The preparation, crystal structure and magnetic properties of a new oxalate-containing copper(II) chain of formula {[(CH3)4N]2[Cu(C2O4)2] · H2O}n (1) [(CH3)4N+ = tetramethylammonium cation] are reported. The structure of 1 consists of anionic oxalate-bridged copper(II) chains, tetramethylammoniun cations and crystallization water molecules. Each copper(II) ion in 1 is surrounded by three oxalate ligands, one being bidentate and the other two exhibiting bis-bidenate coordination modes. Although all the tris-chelated copper(II) units from a given chain exhibit the same helicity, adjacent chains have opposite helicities and then an achiral structure results. Variable-temperature magnetic susceptibility measurements of 1 show the occurrence of a weak ferromagnetic interaction through the oxalate bridge [J = +1.14(1) cm−1, the Hamiltonian being defined as H = –J ∑nmSi · Sj]. This value is analyzed and discussed in the light of available magneto-structural data for oxalate-bridged copper(II) complexes with the same out-of-plane exchange pathway. 相似文献
145.
Laura Vallecillos Francesc Borrull Eva Pocurull 《Journal of separation science》2012,35(20):2735-2742
A method for the quantitative determination of ten musk fragrances extensively used in personal care products from sewage sludge was developed by using a pressurized liquid extraction (PLE) followed by an automated ionic liquid‐based headspace single‐drop microextraction and gas chromatography‐tandem mass spectrometry. The influence of main factors on the efficiency of PLE was studied. For all musks, the highest recovery values were achieved using 1 g of pretreated sewage sludge, H2O/methanol (1:1) as an extraction solvent, a temperature of 80°C, a pressure of 1500 psi, an extraction time of 5 min, 2 cycles, a 100% flush volume, a purge time of 120 s, and 1 g Florisil as in‐cell clean‐up extraction sorbent. The use and optimization of an in‐cell clean‐up sorbent was necessary to remove fatty interferents of the PLE extract that make the subsequent ionic liquid‐based headspace single‐drop microextraction difficult. Validation parameters, namely LODs and LOQs, ranged from 0.5–1.5 to 2.5–5 ng/g, respectively. Good levels of intra‐ and interday repeatabilities were obtained analyzing sewage sludge samples spiked at 10 ng/g (n = 3, RSDs < 10%). The method applicability was tested with sewage sludge from different wastewater treatment plants. The analysis revealed the presence of all the polycyclic musks studied at concentrations higher than the LOQs, ranging from 6 to 530 ng/g. However, the nitro musk concentrations were below the LOQs or, in the case of musk xylene, was not detected. 相似文献
146.
E Pardo C Train H Liu LM Chamoreau B Dkhil K Boubekeur F Lloret K Nakatani H Tokoro S Ohkoshi M Verdaguer 《Angewandte Chemie (International ed. in English)》2012,51(33):8356-8360
Multiferroic materials: A novel class of multiferroics based on organic-inorganic hybrid materials is synthesized. The ferromagnetic properties originate from the coordination network, whereas the ferroelectricity results from the polar organic ions (see picture, M=magnetization and P=polarization). 相似文献
147.
This perspective article focuses on the physical and chemical properties of highly active catalysts for CO oxidation, desulfurization and hydrogenation reactions generated by depositing noble metals on metal-carbide surfaces. To rationalize structure-reactivity relationships for these novel catalysts, well-defined systems are required. High-resolution photoemission, scanning tunneling microscopy (STM) and first-principles periodic density-functional (DF) calculations have been used to study the interaction of metals of Groups 9, 10 and 11 with MC(001) (M = Ti, Zr, V, Mo) surfaces. DF calculations give adsorption energies that range from 2 eV (Cu, Ag, Au) to 6 eV (Co, Rh, Ir). STM images show that Au, Cu, Ni and Pt grow on the carbide substrates forming two-dimensional islands at very low coverage, and three-dimensional islands at medium and large coverages. In many systems, the results of DF calculations point to the preferential formation of admetal-C bonds with significant electronic perturbations in the admetal. TiC(001) and ZrC(001) transfer some electron density to the admetals facilitating bonding of the adatom with electron-acceptor molecules (CO, O(2), C(2)H(4), SO(2), thiophene, etc.). For example, the Cu/TiC(001) and Au/TiC(001) systems are able to cleave both S-O bonds of SO(2) at a temperature as low as 150 K, displaying a reactivity much larger than that of TiC(001) or extended surfaces of bulk copper and gold. At temperatures below 200 K, Au/TiC is able to dissociate O(2) and perform the 2CO + O(2)→ 2CO(2) reaction. Furthermore, in spite of the very poor hydrodesulfurization performance of TiC(001) or Au(111), a Au/TiC(001) surface displays an activity for the hydrodesulfurization of thiophene higher than that of conventional Ni/MoS(x) catalysts. In general, the Au/TiC system is more chemically active than systems generated by depositing Au nanoparticles on oxide surfaces. Thus, metal carbides are excellent supports for enhancing the chemical reactivity of noble metals. 相似文献
148.
Francesc Llerena 《Operations Research Letters》2012,40(2):84-88
In this note we consider the pairwise egalitarian solution (Sánchez-Soriano, 2003) on the domain of assignment games and study its relation with the core. Strengthening the dominant diagonal condition (Solymosi and Raghavan, 2001), we introduce k-dominant diagonal assignment games (k≥1), analyzing for which values of k the pairwise egalitarian solution fulfills the standards of fairness represented by the Lorenz domination and the kernel. We also characterize the Thompson’s fair division point (Thompson, 1981) for arbitrary assignment games. 相似文献
149.
From an Icosahedron to a Plane: Flattening Dodecaiodo‐dodecaborate by Successive Stripping of Iodine
Dr. Pau Farràs Dr. Nina Vankova Lei Liu Zeonjuk Jonas Warneke Dr. Thomas Dülcks Prof. Dr. Thomas Heine Prof. Dr. Clara Viñas Prof. Dr. Francesc Teixidor Prof. Dr. Detlef Gabel 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(41):13208-13212
It has been shown by electrospray ionization–ion‐trap mass spectrometry that B12I122? converts to an intact B12 cluster as a result of successive stripping of single iodine radicals or ions. Herein, the structure and stability of all intermediate B12In? species (n=11 to 1) determined by means of first‐principles calculations are reported. The initial predominant loss of an iodine radical occurs most probably via the triplet state of B12I122?, and the reaction path for loss of an iodide ion from the singlet state crosses that from the triplet state. Experimentally, the boron clusters resulting from B12I122? through loss of either iodide or iodine occur at the same excitation energy in the ion trap. It is shown that the icosahedral B12 unit commonly observed in dodecaborate compounds is destabilized while losing iodine. The boron framework opens to nonicosahedral structures with five to seven iodine atoms left. The temperature of the ions has a considerable influence on the relative stability near the opening of the clusters. The most stable structures with five to seven iodine atoms are neither planar nor icosahedral. 相似文献
150.
Alexandru MG Visinescu D Madalan AM Lloret F Julve M Andruh M 《Inorganic chemistry》2012,51(9):4906-4908
The first 3d-4f-5d heterotrimetallic complexes using [W(V)(bipy)(CN)(6)](-) as a metalloligand were synthesized (bipy = 2,2'-bipyridine). The structural and magnetic properties of three [Cu(II)Ln(III)W(V)] complexes (Ln = Gd, Ho, Tb) are discussed. 相似文献