1,721,033 research outputs found
Reattività di perossocomplessi di V(V).
No full textPerossocomplessi di vanadio(V) sono in grado di ossidare selettivamente alcoli allilici, solfuri e solfossidi organici, ma anche di idrossilare anelli aromatici. Tale spettro di reattività presenta notevoli potenzialità applicative e risvolti meccanicistici di interesse fondamentale. Questi argomenti sono stati affrontati congiuntamente dal gruppo di ricerca dell'Università di Padova in collaborazione con il Prof. John Edwards presso i laboratori della Brown University (RI,USA). In questo lavoro viene presentata una descrizione generale delle problematiche studiate e dei risultati ottenuti
Aldosterone synthase inhibitors for cardiovascular diseases: A comprehensive review of preclinical, clinical and in silico data
Full text linkAldosterone, the main mineralocorticoid hormone, plays a fundamental role in maintaining blood pressure (BP)and volume under hypovolemic conditions. However, in numerous diseases, where it is produced in excess, it plays a detrimental role and contributes to cardiovascular events and ultimately to death in a multitude of patients. The seminal observation that the fungicide-derivative fadrozole blunted steroidogenesis has led to develop several agents to inhibit aldosterone synthase (AS, CYP11B2), the mitochondrial NADH-dependent enzyme that is necessary for aldosterone biosynthesis. Aldosterone synthase inhibitors (ASI) have, thereafter, been conceived and investigated in phase I and phase II studies. We herein reviewed the ASIs available so far considering their chemical structure, the related aldosterone synthase binding and pharmacodynamic properties. We also examined the promising results obtained with ASIs that have already been tested in phase II human studies
Light-Induced Organic Transformations by Covalent Organic Frameworks as Reticular Platforms for Selective Photosynthesis
Full text linkPhotoassisted synthesis of value-added organic products has developed greatly in the last decades in response to the pressing need for a transition toward sustainable processes and renewable energy. One of the formidable challenges of the light-induced chemical steps is provided by the control of the catalytic efficiency and selectivity under photocatalytic conditions. An attractive perspective is foreseen by triggering the photoreaction events in confined spaces, wherein light harvesting and photocatalytic units are framed into functional architectures. Division of tasks among specialized compartments responds to a bioinspired strategy with the final aim to orchestrate the rate of concurrent and sequential events, to maximize performance while directing the reaction selectivity. Covalent organic frameworks (COFs) are a class of emerging materials that can meet these requirements, with the potential to bridge the existing gap between molecular and heterogeneous photocatalysis. Here, a rich pool of molecular building blocks and chemical linkages is available to afford crystalline porous solids with tailored photophysical properties emerging from the interconnected COF structure walls, while catalytic cofactors can be provided by engineering of the pore surface. In this Perspective, we highlight recent developments where COFs have been successfully employed as photocatalysts for selective organic transformations. The relationship between the COF reticular structure and its photocatalytic behavior is discussed, in terms of the light-conversion pathways and photoredox events, including electron and/or energy transfer mechanisms. The possible role of confinement effects, intrinsic in long-range order porous COF materials, remains largely unexplored in photocatalytic applications. New progress is expected to arise from close interdisciplinary cooperation involving synthetic chemistry and materials science communities
Electrocatalytic CO2 reduction: role of the cross-talk at nano-carbon interfaces
Full text linkThe electrocatalytic CO2 reduction reaction (CO2RR) is an interfacial process, involving a minimum of three phases at the contact point of gaseous CO2 with the electrodic surface and the liquid electrolyte. As a consequence, surface chemistry at composite interfaces plays a central role for CO2RR selectivity and catalysis. Each interface defines a functional boundary, where active sites are exposed to a unique environment, with respect to distal sites in the bulk of organic and inorganic domains. While the individual role of each component-type is hardly predictable "a-solo", the interface ensemble works via a strategic interplay of individual effects, including: (i) enhanced electrical conductivity, (ii) high surface area and exposure of the interfacial catalytic sites, (iii) favorable diffusion and feeding of reactants, (iv) complementary interactions for the "on/off" stabilization of cascade intermediates, (v) a secondary sphere assistance to lower the activation energy of bottleneck steps, (vi) a reinforced robustness and long-term operation stability. Selected CO2RR case studies are compared and contrasted to highlight how the organic domains of carbon nanostructures merge with metal and metal-oxide active sites to separate tasks but also to turn them into a cooperative asset of mutual interactions, thus going beyond the classic "Divide et Impera" rule
Electrocatalytic CO2reduction: Role of the cross-talk at nano-carbon interfaces
Full text linkThe electrocatalytic CO2 reduction reaction (CO2RR) is an interfacial process, involving a minimum of three phases at the contact point of gaseous CO2 with the electrodic surface and the liquid electrolyte. As a consequence, surface chemistry at composite interfaces plays a central role for CO2RR selectivity and catalysis. Each interface defines a functional boundary, where active sites are exposed to a unique environment, with respect to distal sites in the bulk of organic and inorganic domains. While the individual role of each component-type is hardly predictable "a-solo", the interface ensemble works via a strategic interplay of individual effects, including: (i) enhanced electrical conductivity, (ii) high surface area and exposure of the interfacial catalytic sites, (iii) favorable diffusion and feeding of reactants, (iv) complementary interactions for the "on/off"stabilization of cascade intermediates, (v) a secondary sphere assistance to lower the activation energy of bottleneck steps, (vi) a reinforced robustness and long-term operation stability. Selected CO2RR case studies are compared and contrasted to highlight how the organic domains of carbon nanostructures merge with metal and metal-oxide active sites to separate tasks but also to turn them into a cooperative asset of mutual interactions, thus going beyond the classic "Divide et Impera"rule
Optically Active Polyoxotungstates Bearing Chiral Organophosphonate Substituents
No full textDivacant Keggin-type polyoxotungstates [γ-XW10O36]8– with X = Si or Ge, were functionalized with chiral phosphoryl groups. The hybrid compounds [(R*PO)2(γ-XW10O36)]4– with R = N-protected aminoalkyl groups or O-protected amino acid derivatives, were isolated. The solution characterization of the products was performed by different techniques: 183W, 31P, 13C, and 1H NMR spectroscopy, electrospray ionization mass spectrometry, UV/Vis spectroscopy, and circular dichroism (CD). The experimental data confirm the covalent grafting of the organic moieties onto the polyanionic surface. A chirality transfer, from the pendant organic arm to the inorganic framework is apparent from CD studies. Multiple Cotton effects were observed in the region of charge-transfer transitions pertaining to W–O bonds. Furthermore, the 183W NMR spectra are consistent with the expected C2 symmetry, resulting from introduction of two organic stereocenters. The title complexes were used in the presence of hydrogen peroxide to perform the oxidation of methyl p-tolyl sulfide. Implications for the design of enantioselective catalysts based on these derivatives are discussed
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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