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101.
Laura Bertani 《Journal of Geometry》1980,15(2):158-169
In this paper,suggested by André's papers ([2), [3]), we construct geometrical structures (X,?,//}) where X is a finite set of points, ? is a set of lines, and // is an equivalence relation on ?. These constructions are made starting with a finite and not empty set X and a permutation group G which is 2-transitive on X and such that the stabilizer of two distinct points of X is different from the identical subgroup. We look for conditions such that the structure (X, ?) is a (3,q)-Steiner system. We remember that a (3,q)-Steiner system is a pair (X,B), where X is a set of elements (called points), B is a system of subsets of X (called blocks), such that:
- every block contains q points exactly;
- given three distinct points x,y,z of X, there is exactly one subset of X belonging to B and containing x,y,z.
102.
103.
Licchelli M Linati L Orbelli Biroli A Perani E Poggi A Sacchi D 《Chemistry (Weinheim an der Bergstrasse, Germany)》2002,8(22):5161-5169
The new quadridentate bischelating ligands 2 and 3 display in solution the typical absorption and emission properties expected for naphthalenediimide derivatives. Spectrophotometric studies show that systems 2 and 3 interact with Zn(II), Cd(II) and Cu(I) in CHCl3 or MeCN according to an apparent 1:1 stoichiometry. Molecular modelling, ESI-MS and 1H NMR experiments indicate that the complex species formed in the presence of stoichiometric amounts of metal ion are nonhelical [2 + 2] adducts. The metal-induced self-assembling process is signalled by an intense excimer-type emission caused by the intramolecular interaction of two naphthalenediimide subunits that face each other in the [2 + 2] adduct, as shown by molecular modelling studies. In the presence of excess metal ion, a disassembling process takes place, leading to a dinuclear complex with a 2:1 metal/ligand stoichiometry, in which the intramolecular excimer is no longer allowed to form because the interaction between the naphthalenediimide subunits has been lost. Thus, the overall metal-induced assembling/disassembling process is signalled by the appearance and disappearance of the excimer band in the emission spectrum. 相似文献
104.
Roitershtein D Domingos A Pereira LC Ascenso JR Marques N 《Inorganic chemistry》2003,42(23):7666-7673
Reaction of yttrium and lanthanum trichloride with 1 equiv of sodium or potassium hydrotris(3,5-dimethylpyrazolyl)borate and 1 equiv of 2,2'-bipyridine gives good yields of the complexes [MCl(2)(Tp(Me2))(C(10)H(8)N(2))] (M = Y (1), La (2)). The analogous compounds with 1,10-phenanthroline, [MCl(2)(Tp(Me2))(C(12)H(8)N(2))] (M = Y (3), La (4)), have been obtained by a similar procedure. The solid-state structures of 2-4 were determined by single-crystal X-ray diffraction and revealed that the compounds are all seven-coordinate with capped octahedral geometry. In contrast, reaction of yttrium trichloride with 1 equiv of sodium hydrotris(3,5-dimethylpyrazolyl)borate in the presence of 1 equiv of neocuproine affords [YCl(3)(Tp(Me2))][Na(neoc)(3))] (5). Compounds 1 and 2 provide an entry for the synthesis of complexes containing the bipyridyl ligand in a radical anionic form or in a dianionic form. Reaction of 1 and 2 with an excess of sodium amalgam gives [Y(Tp(Me2))(bipy)(THF)(2)] (6) and [La(Tp(Me2))(2)(bipy)] (7), respectively. The structures of both compounds have been determined by X-ray crystallography. Compound 7 can be oxidized with iodine to give [La(Tp(Me2))(2)(bipy)]I (8). 相似文献
105.
Favero LB Maris A Esposti AD Favero PG Caminati W Pawelke G 《Chemistry (Weinheim an der Bergstrasse, Germany)》2000,6(16):3018-3025
The rotational spectra of four (GT, TT, TG, and GG) of the five possible conformers of 1-fluorobutane have been assigned by combining free jet and conventional microwave spectroscopy. The geometry optimization was performed at the MP2 (full) level of theory with the 6-31G (d) and 6-311G (d, p) basis sets and by using the B3LYP (3df, 3pd) density functional method. The relative stability of the five rotamers is calculated at the QCISD (T)/6-311G (d, p) level of theory. In spite of the fact that ab initio calculations indicated the unobserved GG' conformer to be more stable than at least one of the observed conformers it was not possible to detect its rotational spectrum. GT and TG are the most and the least stable species, respectively. The rotational spectra of several vibrational satellites of the four conformers have been studied by conventional microwave spectroscopy. The overall conformational equilibrium is governed by the two-dimensional potential energy surface of the skeletal torsions MeC-CC and FC-CC, which have been evaluated by a flexible model analysis, based on the experimental values of the relative conformational and vibrational energy spacings, and on the shifts of second moments of inertia upon conformational change and vibrational excitation. The relative energy of the fifth stable conformer (GG') was determined to be 333 cm(-1) from flexible model calculations, and to be 271 cm(-1) from the most accurate ab initio calculations. 相似文献
106.
The rat liver mitochondrial proteins 总被引:9,自引:0,他引:9
Subcellular fractionation increases the probability of detection of low-abundance proteins. We prepared a fraction highly enriched in mitochondrial proteins from rat liver. The proteins were analyzed by two-dimensional (2-D) electrophoresis using broad-and narrow-range immobilized pH gradient strips, and identified by matrix assisted laser desorption/ionization-mass spectrometry (MALDI-MS). 192 different gene products were detected, of which approximately 70% were enzymes with a broad spectrum of catalytic activities. Most of the identified proteins were detected in other rat protein samples as well, which were analyzed in our laboratory. Eight gene products were detected for the first time. These were represented by one spot each, whereas most of the frequently detected proteins were represented by multiple spots. In average, approximately 10-15 spots corresponded to one gene product. 相似文献
107.
Freiría A Bastida R del Carmen Fernández-Fernández M Macías A Valencia L Vicente M 《Inorganic chemistry》2005,44(4):930-934
We report here the first pentanuclear Ba(II) complex of a new tri-aza, tri-oxa macrocycle with two carboxymethyl "arms" pending from two N atoms, H2L2. The crystal structure corresponds to the formula [Ba5(H0.375L2)4(ClO4)(CH3CH2OH)(H2O)2](ClO4)2.5 x 9.5H2O and reveals the presence of four molecules of the ligand surrounding five Ba(II) ions, giving rise to an unusual structure with the metal ions inside a spherical organic cavity. 相似文献
108.
Romanato Filippo Berti Marina Mazzer Massimo Drigo Antonio Vittorio Lazzarini Laura Franzosi Paolo Salviati Giancarlo Bertone Daniele 《Mikrochimica acta》1994,114(1):431-440
A combined method for structural characterization of strained epitaxial heterostructures involving different techniques such as Rutherford backscattering spectrometry (RBS), multiple crystal X-ray diffractometry (MCD) and transmission electron microscopy (TEM) is presented. In order to obtain a complete characterization of the analysed structure, three different quantities are measured independently: the epilayer thickness, the density of misfit dislocations which may appear at the interface, and the significant components of the strain tensor, mainly the tetragonal distortion, affecting the epilayer lattice. In this way the thermodynamic state and the mechanisms of plastic deformation of the structures can be fully investigated. In this contribution we present and discuss the experimental results concerning a set of InP/GaAs samples having different layer thicknesses ranging from 5 to 500 nm. The thickness of the samples has been determined by RBS. Measurements of in-plane strain and tetragonal distortion have been performed by MCD and RBS-channelling respectively, finally TEM has been used for determining the defects densities and distribution. 相似文献
109.
Laura Masgrau Àngels González-Lafont José M. Lluch 《Theoretical chemistry accounts》2002,108(1):38-40
Variational transition state theory including tunneling corrections (as implemented in Polyrate 8.7) and using multilevel
energy calculations at the MCCM-CCSD(T)-1sc level for the CH4 + OH reaction and at the MCCM-CCSD(T)-2m level for the CD4 + OH process, reproduces very well the experimental rate constants. However, no single methodology was found that reproduces
equally well the experimental rate constants for both title reactions.
Received: 24 March 2002 / Accepted: 11 April 2002 / Published online: 4 July 2002 相似文献
110.
Luisa Fernanda Rojas Paola Zapata Laura Ruiz-Tirado 《Current Opinion in Green and Sustainable Chemistry》2022
According to the Food and Agriculture Organization of the United Nations, approximately 1.3 billion tons of food is wasted each year, equivalent to approximately one-third of world production. Agri-food wastes are the source of proteins, carbohydrates, lipids, and other essential minerals that have been exploited for value-added products by the development of biorefineries and sustainable business as important elements of circular economies. The innovation and materialization of these types of processes, including the use of disruptive technologies on microbial bioconversion and enzyme technology, such as nanotechnology, metabolic engineering, and multi-omics platforms, increase the perspectives on the waste valorization process. Lignocellulolytic enzymes, pectinases, and proteases are mainly used as catalyzers on agri-food waste treatment, and their production in house might be the trend in near future for agro-industrial countries. Another way to transform the agri-food wastes is via aerobic or anaerobic microbial process from fungal or bacterial cultures; these processes are the key to produce waste enzymes. 相似文献