The oxyfunctionalization of 4‐methylcoumarins using dimethyldioxirane

The kinetic study of the efficient regioselective oxidation of the C? C double bond of 4‐methylcoumarins with isolated dimethyldioxirane was investigated using UV–vis spectroscopy methods. In the excess of dimethyldioxirane, the pyrone ring of a coumarin skeleton is selectively epoxidated and hydroxylated in neutral media, in high yields. Kinetic analyses demonstrate two independent reaction pathways, epoxidation and hydroxylation, respectively, which was also confirmed using kinetic isotope effect methods. Both reaction products were isolated, and their structures were determined by NMR and mass spectra. The position of methyl groups attached at the aromatic part of coumarin molecule shows significant influence on kinetic rate constants and activation parameters. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 41: 414–420, 2009     

Enantioselective hydrogenation of polar substrates in inverted supercritical CO2/aqueous biphasic media

An inverted supercritical CO2/aqueous biphasic catalytic system allows highly enantioselective hydrogenation of polar water-soluble substrates and efficient recycling of the CO2-philic catalysts.     

Fast frequency selective MR imaging

With the proposed fast frequency selective MR imaging (FFSMRI) method, we focused on the elimination of all off-resonance components from the image of the observed object. To maintain imaging speed and simultaneously achieve good frequency selectivity, MRI was divided into two steps: signal acquisition and postprocessing. After the preliminary phase in which we determine imaging parameters, MRI takes place; the signal from the same object is successively acquired M times. As a result, we obtain M partial signals in k-space, from which we calculate the image of the observed object in postprocessing phase, after signal acquisition has been completed. With proper selection of parameters, it is possible to exclude from the image a majority of off-resonance components present in the observed object. However, we can decide to keep only a chosen off-resonance component in the image and eliminate all other components, including the on-resonance component and thus producing a different image from the same acquisition. The experiments with Fe(OH)(3) and oil showed that signal-to-noise ratio (SNR) can be improved by about a factor of four. The proposed FFSMRI method is suitable for frequency selective MR imaging and quantitative measurements in dynamic MRI where exclusion of off-resonance components can improve the reliability of measurement.     

Estensioni semigruppali

Sommario Si da un nuovo metodo per costruire algebre da una data algebra, si studiano le identità che si conservano in questa costruzione e l'operatore ad essa collegato.

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Summary I give a new method for building new algebras from a given algebra, we study identities preserved in this construction and related operator.

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Lavoro eseguito nell'ambito dell'attività dei gruppi di ricerca matematica del C.N.R. contratto n. 115218205174.

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Ringrazio il Prof.R. Magari dell'Università di Ferrara sotto la cui guida è stato eseguito questo lavoro.     

Comparing some operational approaches to the limit of detection

The limit of detection is one of the fundamental metrological characteristics of any chemical measurement systems but, even now, it is a highly controversial matter because of the existing differences in terminology, formulations and understanding. Even when limiting the analysis to those operational approaches that, because of their simplicity, are often suggested by the guidelines of some international bodies, the available approaches can return appreciably different estimates. In this paper, the matter is critically reconsidered, and the different approaches compared with the aid of some case studies.     

Sulfanyl-methylene-5(4H)-oxazolones and β-sulfanyl-α-nitroacrylates as appealing dienophiles for the synthesis of conformationally constrained cysteine analogues

A new class of masked constrained cysteine derivatives containing the norbornen/ane scaffold were prepared by the way of Diels–Alder cycloaddition reaction by exploitation of two different dienophiles, sulfanyl-methylene-5(4H)-oxazolones and β-sulfanyl-α-nitroacrylates. The new norbornen/ane amino acid derivatives can be considered versatile building blocks due to the presence of the α,α-disubstituted amino acid function, suitable for peptide synthesis, but also by the carbon–carbon norbornene double bond, which could be variously functionalized.     

Robust portfolio asset allocation and risk measures

Many financial optimization problems involve future values of security prices, interest rates and exchange rates which are not known in advance, but can only be forecast or estimated. Several methodologies have therefore been proposed to handle the uncertainty in financial optimization problems. One such methodology is Robust Statistics, which addresses the problem of making estimates of the uncertain parameters that are insensitive to small variations. A different way to achieve robustness is provided by Robust Optimization, which looks for solutions that will achieve good objective function values for the realization of the uncertain parameters in given uncertainty sets. Robust Optimization thus offers a vehicle to incorporate an estimation of uncertain parameters into the decision making process. This is true, for example, in portfolio asset allocation. Starting with the robust counterparts of the classical mean-variance and minimum-variance portfolio optimization problems, in this paper we review several mathematical models, and related algorithmic approaches, that have recently been proposed to address uncertainty in portfolio asset allocation, focusing on Robust Optimization methodology. We also give an overview of some of the computational results that have been obtained with the described approaches. In addition we analyze the relationship between the concepts of robustness and convex risk measures.