1,721,415 research outputs found
Solvability of some boundary value problems involving p-Laplacian and non-autonomous differential operators
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New Perspectives in the Indole Ring Functionalization using 2-Indolylmethanols
Full text link2-Indolylmethanols have been recently involved in several processes dealing with indole functionalization.
These compounds, upon activation by Brønsted or Lewis acids, generate a bidentate electrophilic system amenable to react at the 3-position or at the benzylic site with a wide range of nucleophilic reagents. The functionalization pattern is affected by the nature of the substituents at the carbinol unit and also depends on the nature of the nucleophile used. Nucleophilic reactants bearing a remote electrophilic site in their structure can be involved in a further ring closure ultimately leading to polycyclic derivatives. This review article summarizes some fundamental aspects of the chemistry of 2-indolylmethanols with particular attention to those related to asymmetric synthesis
Synthesis and practical applications of 2-(2-nitroalkyl)pyrroles
No full textFunctionalization of pyrroles introducing a 2-nitroalkyl moiety allows the formation of nitro-containing compounds to be used as pivotal intermediates for the synthesis of bioactive compounds. Reaction of pyrroles with nitroalkenes under the Friedel–Crafts conditions, allows a direct entry to 2-(2-nitroalkyl) pyrroles. This approach can be also used for the preparation of enantioenriched derivatives exploiting asymmetric catalysis. In a complementary fashion, the Henry reaction between 2-formylpyrroles and nitroalkanes generates the corresponding nitroaldol products which upon dehydration and reduction of the intermediate 2-pyrrolylnitroethene efficiently afford 2-(2-nitroalkyl) pyrroles. This review article summarizes the most relevant procedures for the preparation of 2-(2-nitroalkyl) pyrroles during the last two decades as well as their significant practical applications
AdS RG-flow and the Super-Yang-Mills cascade
No full textWe study the 5 dimensional SUGRA AdS duals of N=4, N=2 and N=1 Super-Yang-Mills theories. To sequentially break the N=4 theory mass terms are introduced that correspond, via the duality, to scalar VEVs in the SUGRA. We determine the appropriate scalar potential and study solutions of the equations of motion that correspond to RG flows in the field theories. Analysis of the potential at the end of the RG flows distinguishes the flows appropriate to the field theory expectations. As already identified in the literature, the dual to the N=2 theory has flows corresponding to the moduli space of the field theory. When the N=2 theory is broken to N=1 the single flow corresponding to the singular point on the N=2 moduli space is picked out as the vacuum. As the N=2 breaking mass scale is increased the vacuum deforms smoothly to previously analysed N=1 flows
Synthetic Approaches to the Challenging Direct C-Alkylation and C-Allylation of Unactivated Nitroalkanes
Full text linkThe limited nucleophilic character and the bidentate nature of unactivated nitroalkane anions (nitronates) makes the corresponding alkylation and allylation procedures rather troublesome. This aspect is in sharp contrast with other commonly employed processes involving nitronate anions such as conjugate additions or nitroaldol reactions. This review summarizes the most rewarding approaches that along the years have been devised to overcome this limitation. Efficient methods are nowadays mainly based on metal-catalyzed processes involving purely ionic or mixed ionic-radical intermediates including photoenzymatic reactions
Gubbio - La Platea Comunis
No full textLo studio prende in esame l’originario assetto medievale e le principali trasformazioni del principale spazio urbano della città di Gubbio, costituito dalla piazza Comunale (“platea Comunis”). Dell’opera, in particolare, sono prese in esame le proporzioni geometriche che definiscono la pianta della piazza e il prospetto del Palazzo dei Consoli, entrambi basati sul “rettangolo aureo”.The study examines the original medieval arrangement and the transformations of the main urban area of the city of Gubbio, consisting of the Piazza Comunale ("platea Comunis"). In particular, are considered the geometrical dimensions that define the plan of the square and the façade of the Palazzo dei Consoli, both based on the "golden rectangle"
Polarization-transparent FSR-free microring resonator filter with wide hitless tunability
No full textA coupled microring resonator architecture with non-integer Vernier ratio design and controllable loss is exploited to implement a polarization-transparent hitless tunable FSR-free filter operating over the extended C+L band (1520 nm-1620 nm). (C) 2021 The Author(s
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
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