Kondo effect in nanostructures

Kondo effect arises whenever a coupling to the Fermi gas induces transitions within the otherwise degenerate ground state multiplet of an interacting system. Both coupling to the Fermi gas and interactions are naturally present in any nanoscale transport experiment. At the same time, many nanostructures can easily be tuned to the vicinity of a degeneracy point. This is why the Kondo effect in its various forms often influences the low temperature transport in meso- and nanoscale systems. In this short review we discuss the basic physics of the Kondo effect and its manifestations in the low-temperature electronic transport through a single electron transistor

Essais sur bouche à oreille électronique : Une revue multidisciplinaire de dimensions, la communication académique et implications commerciales

Cette thèse explore le concept, l’état de la littérature, et les implications commerciales de la bouche-a-oreille électronique (eWOM). Elle est basée sur un article conceptuel et deux articles empiriques. Dans le premier essai, j’apporte une clarification conceptuelle en mettant en évidence la multidimensionnalité du concept qui comporte cinq aspects (qui, quoi, où, quand et comment). Dans le second essai, le modèle résultant du premier essai est suivi d'une analyse historique des dimensions, terminologies équivalentes, théories et méthodes utilisées dans la recherche existante pour étudier l’eWOM.Utilisant l'analyse de réseau de citations, j’identifie des lacunes dans la littérature scientifique afin de faciliter la construction progressive de connaissances dans ce domaine. Enfin, dans le troisième essai, j'utilise une méta-analyse pour tester empiriquement les effets modérateurs de quatre des cinq dimensions de l’eWOM sur l'efficacité des ventes. J’observe que l’eWOM est corrélé positivement avec les ventes (.091), mais que son efficacité diffère grandement en fonction de la plateforme, du produit considéré et des mesures utilisées. Les implications théoriques et managériales, ainsi que des pistes de futures recherches, sont discutées.This dissertation explores the construct, prior scientific inquiry, and market implications of electronic word of mouth (eWOM), and it is based upon one conceptual and two empirical papers. In the first essay, I provide conceptual clarity by dimensionalizing the construct according to five aspects (the Who, What, Where, When, and How of eWOM). In the second essay, the resulting organizing framework is followed up with a historical analysis of eWOM dimensions, aliases, theories, and methodologies used in prior research.Additionally, I employ citation network analysis in order to identify gaps in scholarly communication and facilitate progressive knowledge building in this area. Finally, in the third essay, I use meta-analysis to empirically test the moderating impact of four of the five eWOM dimensions on sales effectiveness. I find that eWOM is positively correlated with sales (.091), but its effectiveness differs across platform, product, and metric factors. Theoretical and practical implications, as well as avenues for further research are discussed

Elliptical Symmetry Tests in R

The assumption of elliptical symmetry has an important role in many theoretical develop ments and applications. Hence, it is of primary importance to be able to test whether that assumption actually holds true or not. Various tests have been proposed in the literature for this problem. To the best of our knowledge, none of them has been implemented in R. This article describes the R package elliptical symmetry which implements several well-known tests for elliptical symmetry together with some recent tests. We demonstrate the testing procedures with a real data example

Aging and Ball-Milling as Low-Energy and Environmentally Friendly Methods for the Synthesis of Pd(II) Photosensitizers

Simple and efficient solid-state synthetic methods, aging and ball milling (liquid-assisted grinding, LAG), have been employed to achieve reactions of triphenylphosphine (tpp) and 1,1′-bis­(diphenylphosphino)­ferrocene (dppf) with dicyclopalladated azobenzenes (DMF)­PdCl­(μ-R¹C₆H₃NNC₆H₃R²)­PdCl­(DMF), R¹ = H, OCH₃, N­(CH₃)₂ and R² = H, NO₂. For the first time the aging processes have been applied in the formation of Pd­(II) heteroleptic complexes. Both synthetic procedures lead to four types of tetra- or pentacoordinated complexes (tpp)­PdCl­{(μ-Cl)­(μ-R¹C₆H₃NNC₆H₃R²)}­Pd­(tpp) <b>1A</b>–<b>3A</b>, (tpp)₂PdCl­(μ-R¹C₆H₃NNC₆H₃R²)­PdCl­(tpp)₂ <b>1B</b>–<b>3B</b>, PdCl­{(μ-Cl)­(μ-R¹C₆H₃NNC₆H₃R²)}­Pd­(dppf) <b>1C</b>–<b>3C</b>, and (dppf)­PdCl­(μ-R¹C₆H₃NNC₆H₃R²)­PdCl­(dppf) <b>1D</b>–<b>3D</b>, in which azobenzenes simultaneously act as monodentate <i>C</i>- and bidentate <i>C</i>,<i>N</i>-donors (<b>A</b>, <b>B</b>, and <b>C</b> complexes) or, for the first time, only as double <i>C</i>-donors (<b>D</b> complexes). Although their formation requires complex intramolecular transformations, aging and ball milling have been proved to be efficient synthetic methods. All products have been fully characterized in solid state and solution. Solid-state structures of complexes have been resolved by a single crystal or powder X-ray diffraction (PXRD) and solid-state NMR spectroscopy. Their electronic structures have been rationalized by the quantum-chemical calculations. The structural features of complexes and their stability in solutions have been evaluated by ¹H and ³¹P NMR spectroscopy along with the ESI-MS spectrometry. The absorption and emission properties of complexes have been studied, and the nature of their electronic transitions in the low energy region has been examined by TD-DFT calculations. Significant fluorescence observed for the complexes with 4-dimethylamino-4′-nitroazobenzene ligand at room temperature in solid state and/or in the solution makes them interesting for potential applications as photoactive units in optical devices

Aging and Ball-Milling as Low-Energy and Environmentally Friendly Methods for the Synthesis of Pd(II) Photosensitizers

Simple and efficient solid-state synthetic methods, aging and ball milling (liquid-assisted grinding, LAG), have been employed to achieve reactions of triphenylphosphine (tpp) and 1,1′-bis­(diphenylphosphino)­ferrocene (dppf) with dicyclopalladated azobenzenes (DMF)­PdCl­(μ-R¹C₆H₃NNC₆H₃R²)­PdCl­(DMF), R¹ = H, OCH₃, N­(CH₃)₂ and R² = H, NO₂. For the first time the aging processes have been applied in the formation of Pd­(II) heteroleptic complexes. Both synthetic procedures lead to four types of tetra- or pentacoordinated complexes (tpp)­PdCl­{(μ-Cl)­(μ-R¹C₆H₃NNC₆H₃R²)}­Pd­(tpp) <b>1A</b>–<b>3A</b>, (tpp)₂PdCl­(μ-R¹C₆H₃NNC₆H₃R²)­PdCl­(tpp)₂ <b>1B</b>–<b>3B</b>, PdCl­{(μ-Cl)­(μ-R¹C₆H₃NNC₆H₃R²)}­Pd­(dppf) <b>1C</b>–<b>3C</b>, and (dppf)­PdCl­(μ-R¹C₆H₃NNC₆H₃R²)­PdCl­(dppf) <b>1D</b>–<b>3D</b>, in which azobenzenes simultaneously act as monodentate <i>C</i>- and bidentate <i>C</i>,<i>N</i>-donors (<b>A</b>, <b>B</b>, and <b>C</b> complexes) or, for the first time, only as double <i>C</i>-donors (<b>D</b> complexes). Although their formation requires complex intramolecular transformations, aging and ball milling have been proved to be efficient synthetic methods. All products have been fully characterized in solid state and solution. Solid-state structures of complexes have been resolved by a single crystal or powder X-ray diffraction (PXRD) and solid-state NMR spectroscopy. Their electronic structures have been rationalized by the quantum-chemical calculations. The structural features of complexes and their stability in solutions have been evaluated by ¹H and ³¹P NMR spectroscopy along with the ESI-MS spectrometry. The absorption and emission properties of complexes have been studied, and the nature of their electronic transitions in the low energy region has been examined by TD-DFT calculations. Significant fluorescence observed for the complexes with 4-dimethylamino-4′-nitroazobenzene ligand at room temperature in solid state and/or in the solution makes them interesting for potential applications as photoactive units in optical devices

Computational Tale of Two Enzymes: Glycerol Dehydration With or Without B₁₂

We present a series of QM/MM calculations aimed at understanding the mechanism of the biological dehydration of glycerol. Strikingly and unusually, this process is catalyzed by two different radical enzymes, one of which is a coenzyme-B₁₂-dependent enzyme and the other which is a coenzyme-B₁₂-independent enzyme. We show that glycerol dehydration in the presence of the coenzyme-B₁₂-dependent enzyme proceeds via a 1,2-OH shift, which benefits from a significant catalytic reduction in the barrier. In contrast, the same reaction in the presence of the coenzyme-B₁₂-independent enzyme is unlikely to involve the 1,2-OH shift; instead, a strong preference for direct loss of water from a radical intermediate is indicated. We show that this preference, and ultimately the evolution of such enzymes, is strongly linked with the reactivities of the species responsible for abstracting a hydrogen atom from the substrate. It appears that the hydrogen-reabstraction step involving the product-related radical is fundamental to the mechanistic preference. The unconventional 1,2-OH shift seems to be required to generate a product-related radical of sufficient reactivity to cleave the relatively inactive C–H bond arising from the B₁₂ cofactor. In the absence of B₁₂, it is the relatively weak S–H bond of a cysteine residue that must be homolyzed. Such a transformation is much less demanding, and its inclusion apparently enables a simpler overall dehydration mechanism

Nanocrystalline CeO_2−δ as Effective Adsorbent of Azo Dyes

Ultrafine CeO_2−δ nanopowder, prepared by a simple and cost-effective self-propagating room temperature synthesis method (SPRT), showed high adsorption capability for removal of different azo dyes. Batch type of adsorption experiments with fixed initial pH value were conducted for the removal of Reactive Orange 16 (RO16), Methyl Orange (MO), and Mordant Blue 9 (MB9). The equilibrium adsorption data were evaluated using Freundlich and Langmuir isotherm models. The Langmuir model slightly better describes isotherm data for RO16 and MO, whereas the Freundlich model was found to best fit the isotherm data for MB9 over the whole concentration range. The maximum adsorption capacities, determined from isotherm data for MO, MB9, and RO16 were 113, 101, and 91 mg g^–1 respectively. The adsorption process follows the pseudo-second-order kinetic model indicating the coexistence of chemisorption and physisorption. The mechanism of azo dye adsorption is also discussed