Search results for "Caliza"
showing 10 items of 656 documents
GFP immunogold staining, from light to electron microscopy, in mammalian cells.
2012
GFP has emerged as an important reporter for monitoring gene expression, protein localization, cell transformation and cell lineage. The development of GFP as a marker in many different biological systems has emphasized the need to image GFP at high resolution. GFP immunogold labeling with colloidal gold particles becomes essential for electron microscopy (EM) ultrastructural detection. Because of the small size, colloidal gold particles require silver enhancement, a procedure to increase the size of the particle as well as gold toning to stabilize the silver layer. GFP preembedding immunogold staining enables high quality cellular-ultrastructural EM analysis mainly for two reasons, on one …
Random walk approach to the analytic solution of random systems with multiplicative noise—The Anderson localization problem
2006
We discuss here in detail a new analytical random walk approach to calculating the phase-diagram for spatially extended systems with multiplicative noise. We use the Anderson localization problem as an example. The transition from delocalized to localized states is treated as a generalized diffusion with a noise-induced first-order phase transition. The generalized diffusion manifests itself in the divergence of averages of wavefunctions (correlators). This divergence is controlled by the Lyapunov exponent $\gamma$, which is the inverse of the localization length, $\xi=1/\gamma$. The appearance of the generalized diffusion arises due to the instability of a fundamental mode corresponding to…
Anderson localization problem: An exact solution for 2-D anisotropic systems
2007
Our previous results [J.Phys.: Condens. Matter 14 (2002) 13777] dealing with the analytical solution of the two-dimensional (2-D) Anderson localization problem due to disorder is generalized for anisotropic systems (two different hopping matrix elements in transverse directions). We discuss the mathematical nature of the metal-insulator phase transition which occurs in the 2-D case, in contrast to the 1-D case, where such a phase transition does not occur. In anisotropic systems two localization lengths arise instead of one length only.
Electron correlation in metal clusters, quantum dots and quantum rings
2009
This short review presents a few case studies of finite electron systems for which strong correlations play a dominant role. In simple metal clusters, the valence electrons determine stability and shape of the clusters. The ionic skeleton of alkali metals is soft, and cluster geometries are often solely determined by electron correlations. In quantum dots and rings, the electrons may be confined by an external electrostatic potential, formed by a gated heterostructure. In the low density limit, the electrons may form so-called Wigner molecules, for which the many-body quantum spectra reveal the classical vibration modes. High rotational states increase the tendency for the electrons to loca…
Synthesis and structure of charge transfer salts of tetrathiafulvalene (TTF) and tetramethyl-TTF with 2,4,7-trinitro and 2,4,5,7-tetranitro-9-fluoren…
2009
Charge transfer salts of tetrathiafulvalene (TTF) and tetramethyltetrathiafulvalene (TMTTF) with the organic acceptors 2,4,7-trinitro-9-fluorenone and 2,4,5,7-tetranitro-9-fluorenone have been prepared and characterized. The compounds (TTF)(TENF) (1), (TTF)3(TRNF)2 (2) and (TMTTF)(TRNF) (3) contain mixed stacks of alternating TTF and nitrofluorenone units. Surprisingly, the degree of charge transfer that occurs in these salts is not controlled solely by the redox potentials of the building blocks, but apparently also by the most effective intermolecular interactions in the solid, as determined from the crystal struc- tures obtained. These three compounds exhibit poor electron delocalization…
Understanding the molecular mechanism of the [3 + 2] cycloaddition reaction of benzonitrile oxide toward electron-richN-vinylpyrrole: a DFT study
2016
The [3 + 2] cycloaddition (32CA) reaction of benzonitrile oxide, BNO 2, with an electron-rich N-vinylpyrrole derivative, NVP 3a, in the presence of dichloromethane, has been theoretically studied using density functional theory (DFT) methods at the B3LYP/6-31G(d) level. This 32CA reaction presents a relatively high activation Gibbs free energy as a result of the low polar character of this zwitterionic-type (zw-type) reaction. Analyses of the calculated relative Gibbs free energies and transition state geometries indicate that the studied 32CA reaction, in excellent agreement with experimental outcomes, takes place in a complete regioselective manner as a consequence of the steric repulsion…
Unveiling the Ionic Diels-Alder Reactions within the Molecular Electron Density Theory
2021
The ionic Diels–Alder (I-DA) reactions of a series of six iminium cations with cyclopentadiene have been studied within the Molecular Electron Density Theory (MEDT). The superelectrophilic character of iminium cations, ω >
Gold(I) Complexes of Ferrocenyl Polyphosphines: Aurophilic Gold Chloride Formation and Phosphine-Concerted Shuttling of a Dinuclear [ClAu···AuCl] Fra…
2016
International audience; A smart steric control of the metallocene backbone in bis- and poly(phosphino)ferrocene ligands favors intramolecular aurophilic interactions between [AuCl] fragments in polynuclear gold(I) complexes. We synthesized and characterized by multinuclear NMR and X-ray diffraction analysis mono-, di-, and polynuclear gold complexes of constrained ferrocenyl diphosphines, which bear either bulky tert-butyl groups or more flexible siloxane substituents at the cyclopentadienyl rings. The complexes meso-1,1'-bis-(diphenylphosphino)-3,3'-di-tert-butylferrocene (4-m), rac-1,1'-bis[bis-(5-methy1-2-furyl)phosphino]-3,3'-di-tert-butyfferrocene (5-r), and rac-1,1'-bis ( diphenylphos…
MULTIPLE CRACKS LOCALIZATION FOR THIN COATING FILM LAYERS IN PURE BENDING
2018
Recently, accurate small scale four-point bending flexural tests, for superalloy specimens with multiple ceramic type external coating film layers, have shown that under high loading, the failure mechanism is characterized by the development of complex multiple surface cracks, followed by interior interlayers debonding mechanisms. The final stage is then the complete debonding of the fragmented thermal coating, which leave the interior superalloy completely uncoated. The mechanical problem has an high technological relevance, since failure, or just severe damage, of the ceramic coating, can jeopardize the functionality of structural elements working at high temperature and under severe load…
Strain localization and crack propagation in finite elements augmented with embedded interphases
2022
Many engineering problems present the need to model discontinuities that arise when materials are outside their elastic limit. In quasi-brittle materials strains progressively localize in narrow bands, usually leaving elastic the surrounding bulk material. In the framework of FE models, considerable progresses have been done in order to correctly model strain localization and damage propagation; they could be mainly divided into two groups: discrete crack models and smeared crack models. In the ambit of discrete crack models, we propose a computational methodology which is based on the Augmented-Finite Element Method (A-FEM) [1]. Our formulation consists in the implementation of an intra-el…